Suspicious Minds

Clinical Psychology Review 27 (2007) 425–457

Suspicious minds: The psychology of persecutory delusions

Daniel Freeman

Department of Psychology, PO Box 77, Institute of Psychiatry, King’s College London, Denmark Hill, London, SE5 8AF, UK

Received 6 July 2006; accepted 10 October 2006

Abstract

At least 10–15% of the general population regularly experience paranoid thoughts and persecutory delusions are a frequentsymptom of psychosis. Persecutory ideation is a key topic for study. In this article the empirical literature on psychologicalprocesses associated with persecutory thinking in clinical and non-clinical populations is comprehensively reviewed. There is alarge direct affective contribution to the experience. In particular, anxiety affects the content, distress and persistence of paranoia. Inthe majority of cases paranoia does not serve a defensive function, but instead builds on interpersonal concerns conscious to theperson. However, affect alone is not sufficient to produce paranoid experiences. There is also evidence that anomalous internalexperiences may be important in leading to odd thought content and that a jumping to conclusions reasoning bias is present inindividuals with persecutory delusions. Theory of mind functioning has received particular research attention recently but thefindings do not support a specific association with paranoia. The threat anticipation cognitive model of persecutory delusions ispresented, in which persecutory delusions are hypothesised to arise from an interaction of emotional processes, anomalousexperiences and reasoning biases. Ten key future research questions are identified, including the need for researchers to considerfactors important to the different dimensions of delusional experience.© 2006 Elsevier Ltd. All rights reserved.

Keywords: Delusions; Paranoia; Cognitive; Schizophrenia; Psychosis

1. Introduction

We are living in paranoid times, with fears of others attaining a new intensity. Nonetheless, being overly wary of theintentions of others has long been recognised as a problem. In the seventeenth century Francis Bacon (1612), oftencredited as the founder of the scientific method, commented on the corrosive nature of the experience: ‘Suspicionsamongst thoughts are like bats amongst birds,— they ever fly by twilight. Certainly they are to be repressed, or, at theleast, well guarded. For they cloud the mind, they lose friends, and they check with business, whereby business cannotgo on currently and constantly. They dispose kings to tyranny, husbands to jealousy, wise men to irresolution andmelancholy.’

Yet in the last 10 years there has been a rapid development in the understanding of persecutory thinking, assisted bythe focus on it as a phenomenon of interest in its own right rather than simply as a symptom of severe mental illness(Bentall, 1990). The argument that will be put forward in this review is that there is now an excellent opportunity to

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426 D. Freeman / Clinical Psychology Review 27 (2007) 425–457

take the starting point of this work of the last 10 years and make dramatic increases in the understanding of persecutorythinking. Explanatory models can become as powerful as those for emotional disorders and lead to more effectivepsychological interventions for paranoia. But also emphasised are the significant conceptual and methodologicallimitations of previous work.

2. The definition of persecutory delusions

There have, of course, been many commentaries on the limitations of definitions of delusional beliefs in general, inthat most criteria do not apply to all delusions, which partly results from epistemological difficulties in determining thereferent of a name by a single set of necessary or sufficient characteristics (see Kripke, 1980). This has all too oftenbeen a rarefied academic debate without consideration of the implications for research or clinical practice.

The most sustainable position is that of Oltmanns (1988). Assessing the presence of a delusion may best beaccomplished by considering a list of characteristics or dimensions, none of which is necessary or sufficient, that withincreasing endorsement produces greater agreement on the presence of a delusion. For instance, the more a belief isimplausible, unfounded, strongly held, not shared by others, distressing and preoccupying then the more likely it is tobe considered a delusion. The practical importance of the debate about defining delusions is that it informs us that thereis individual variability in the characteristics of delusional experience (see Table 1). Delusions are definitely notdiscrete discontinuous entities. They are complex, multi-dimensional phenomena (Garety & Hemsley, 1994). Theimplication is that there can be no simple answer to the question ‘What causes a delusion?’ Instead, an understanding ofeach dimension of delusional experience is needed: what causes the content of a delusion? What causes the degree ofbelief conviction? What causes resistance to change? What causes the distress? It is plausible that different factors areinvolved in different dimensions of delusional experience. Research on the causes of different dimensions of delusionalexperience is rare; a few studies consider delusional conviction (Freeman et al., 2004; Garety et al., 2005) anddelusional distress (Freeman & Garety, 1999; Freeman, Garety, & Kuipers, 2001; Startup, Freeman, & Garety, inpress). The implication for clinical practice is that clinicians need to think with clients about the aspect of delusionalexperience they are hoping will change during the course of an intervention (see Birchwood & Trower, 2006) andformulate accordingly.

In contrast to the debates about defining delusions, diagnostic criteria for sub-types of delusional beliefs based uponcontent have not been a topic of comment. Many reports of studies are unclear about the definition of persecutorydelusions used. This is perhaps because the issue is thought to be self-evident, but it is more complex than might be

Table 1The multi-dimensional nature of delusions

Characteristic ofdelusions

Variability in characteristic

Unfounded For some individuals the delusions reflect a kernel of truth that has been exaggerated (e.g. the person had a dispute with theneighbour but now believes that the whole neighbourhood is monitoring them and will harm them). It can be difficult todetermine whether the person is actually delusional. For others the ideas are fantastic, impossible and clearly unfounded (e.g.the person believes that s/he was present at the time of the Big Bang and is involved in battles across the universe andheavens).

Firmly held Beliefs can vary from being held with 100% conviction to only occasionally being believed when the person is in a particularstressful situation.

Resistant to change An individual may be certain that they could not be mistaken and will not countenance any alternative explanation for theirexperiences. Others feel very confused and uncertain about their ideas and readily want to think about alternative accounts oftheir experiences.

Preoccupying Some people report that they can do nothing but think about their delusional concerns. For other people, although they firmlybelieve the delusion, such thoughts rarely come into their mind.

Distressing Many beliefs, especially those seen in clinical practice, are very distressing (e.g. persecutory delusions) but others (e.g.grandiose delusions) can actually be experienced positively. Even some persecutory delusions can be associated with lowlevels of distress (e.g. the individual believes that the persecutor hasn't the power to harm them).

Interferes withsocial functioning

Delusions can stop people interacting with others and lead to great isolation and abandonment of activities. Other people canhave a delusion and still function at a high level including maintaining relationships and employment.

Involves personalreference

In many instances the patient is at the centre of the delusional system (e.g. ‘I have been singled out for persecution’). Howeverfriends and relatives can be involved (e.g. ‘They are targeting my whole family’) and some people believe that everybody isaffected equally (e.g. ‘Everybody is being experimented upon’).

Table 2Criteria for a delusion to be classified as persecutory (Freeman & Garety, 2000)

Criteria A and B must be met:A. The individual believes that harm is occurring, or is going to occur, to him or her.B. The individual believes that the persecutor has the intention to cause harm.

There are a number of points of clarification:Harm concerns any action that leads to the individual experiencing distress.Harm only to friends or relatives does not count as a persecutory belief, unless the persecutor also intends this to have a negative effect upon theindividual.The individual must believe that the persecutor at present or in the future will attempt to harm him or her.Delusions of reference do not count within the category of persecutory beliefs.

427D. Freeman / Clinical Psychology Review 27 (2007) 425–457

considered at first sight. There is great variety in the content of persecutory thoughts, for instance, in the type andtiming of threat, the target of the harm, and the identity and intention of the persecutor (Freeman et al., 2001).Furthermore, terms such as paranoia, delusions of persecution, and delusions of reference have been used inter-changeably and to refer to different concepts. Freeman and Garety (2000) clarify the definition of persecutory ideation:the individual believes that harm is occurring, or is going to occur, to him or her, and that the persecutor has theintention to cause harm (see Table 2). The second element of the definition distinguishes persecutory from anxiousthoughts. Use of clear criteria such as these, coupled with descriptions of the levels of conviction and distress inparticipant groups, will enable both a focus on pure phenomena and comparisons across research studies.

3. The epidemiology of paranoid thinking

Surprisingly, the epidemiology of persecutory ideation has not been systematically reviewed. Basic information onthe prevalence and distribution of paranoid thoughts is key in determining the importance of the experience and themost appropriate research strategy. This neglected area will therefore be given some consideration.

Persecutory delusions, as most people are aware, are taken as a key sign of severe mental illnesses such asschizophrenia. Sartorius et al. (1986) present findings from a World Health Organisation prospective study in tencountries of individuals with signs of schizophrenia making first contact with services (N=1379). Persecutorydelusions were the second most common symptom of psychosis, after delusions of reference, occurring in almost 50%of cases. However, there are many other diagnoses in which persecutory delusions occur in a substantial minority. Thepresence of delusions and hallucinations in unipolar depression is approximately 15% (Johnson, Horwath, &Weissman, 1991). Again, persecutory beliefs are a common presentation of these delusions: a case-note review byFrangos, Athanassenas, Tsitourides, Psilolignos, and Katsanou (1983) found that 44% of patients with unipolardepressive psychosis (N=136) had persecutory delusions. In a review of bipolar disorder, Goodwin and Jamison(1990) suggest that persecutory delusions (28%) are frequent in manic episodes. There is evidence from small-scaleclinical studies that psychotic symptoms occur in approximately 30% of cases of combat-related PTSD (Butler,Mueser, Sprock, & Braff, 1996; Hamner, Freuch, Ulmer, & Arana, 1999). Hallucinations are the most commonpsychotic symptom associated with PTSD, but delusions also occur, particularly with a persecutory theme. Persecutoryideation is of course likely to be common in paranoid personality disorder, the main criterion for which is that theperson has ‘a pervasive distrust and suspiciousness of others such that their motives are interpreted as malevolent’(DSM-IV; APA, 1994). It is also of note that people with anxiety or depression have elevated scores on measures ofpersecutory ideation (Van Os et al., 1999). Finally, persecutory delusions occur in neurological disorders, such asdementia (Flint, 1991) and epilepsy (Trimble, 1992). For instance, Rubin, Drevets, and Burke (1988) report that 31% of110 individuals with dementia of the Alzheimer type had paranoid delusions.

Many have argued that psychotic symptoms such as delusions might be better understood on a continuum withnormal experience (Chapman & Chapman, 1980; Claridge, 1997; Johns, 2005; Peters, Joseph, & Garety, 1999; Van Os& Verdoux, 2003; Strauss, 1969). Delusions in psychosis would represent the severe end of a continuum, but suchexperiences would be present, often to a lesser degree, in the general population, and this would be related to milderattenuated forms of the experience. For example, a clinical persecutory delusion about government attempts to kill theperson would be considered related to non-clinical delusions about neighbours trying to get at the person that would inturn be considered as related to everyday suspicions about the intentions of others. However, it should be emphasisedthat there are different forms of the continuum view (Claridge, 1994) and the distribution of symptoms may well be

Table 3Studies of paranoid thinking in non-clinical populations

Study N Assessment Time period Prevalence

Representative general population studiesEpidemiologicCatchment Area(EPA) programEaton et al. (1991)

810 adults in Baltimore,United States (weightedfor larger population of3481 from which thissub-sample was drawn)

Diagnostic InterviewSchedule (Robins et al.,1981). This schedulewas not administered bya mental health professional.

Pastmonth

Symptom endorsement is reported firstfollowed by clinical symptom level in bracketsPeople spying on you 12% (1%)People following you 8% (1%)Trying to hurt you 5% (1%)Reading your mind 2% (1%)Others control you 2% (2%)Steal thoughts 2% (1%)

Epidemiologic CatchmentArea (EPA) programprospective study

Tien and Anthony(1990)

4994 adults (aged 18 to49 years) were selectedfrom the US survey whohad not reported anypsychotic symptoms atthe baseline assessment.They were then assessed1 year later.

Diagnostic InterviewSchedule (Robins et al.,1981). This schedulewas not administered bya mental health professional.

Newoccurrenceofsymptomsin the pastyear.

New symptom onset:Believed people were watching you

or spying on you? 2.6%Believed people were following you? 1.6%Believed someone was plotting against

you or trying to hurt you or poisonyou? 0.5%

Believed someone was reading yourmind? 0.6%

Believed others were controlling how youmoved or what you thought against yourwill? 0.3%

Felt that someone or something could putstrange thoughts directly into your mind of couldtake or steal thoughts out of your mind? 0.2%

2000 British NationalSurvey of PsychiatricMorbidity Johns et al.(2004)

8580 adults in theUnited Kingdom(aged 16–74) (60individuals withpsychosis were thenexcluded)

Psychosis ScreeningQuestionnaire (Bebbington& Nayani, 1995). Notadministered bymental health professional.

Past year ParanoiaOver the past year, have there been times

when you felt that people were against you?21.2%

Have there been times when you felt thatpeople were deliberately acting to harm youor your interests? 9.1%

Have there been times when you felt thata group of people were plotting to cause youserious harm or injury? 1.5%Thought insertion

Over the past year, have you ever felt thatyour thoughts were directly interfered withor controlled by some outside force orperson? 9.0%

Did this come about in a way that manypeople would find hard to believe, forinstance, through telepathy? 0.9%

Representative older adult general population studiesOlder AmericanResources andServices (OARS) —Durham surveyChristenson andBlazer (1984)

997 adults (aged 65+)in Durham County,N.C., USA

Mini-Mult(Kincannon, 1968)

For total group ‘generalised persecutoryideation’ 4%For group without cognitive impairment(N=781)‘Generalised persecutory ideation’ 2%

Kungsholmen projectForsell andHenderson (1998)

1420 adults (aged 75+)in Stockholm, Sweden.People living in all typesof institutions were alsoincluded.

ComprehensivePsychopathological RatingScale (CPRS) (Äsberg et al.,1978). Assessment by mentalhealth professional.

6.3% had paranoid symptom.For individuals without cognitiveimpairment the prevalence was 2.6%


Table 3 (continued )

Study N Assessment Time period Prevalence

Representative older adult general population studiesLongitudinal

Gerontological andGeriatric PopulationStudy Östling andSkoog (2002)

347 adults (aged 85)without dementiarepresentative of abirth cohort in Göteborg,Sweden.

ComprehensivePsychopathological RatingScale (Äsberg et al.,1978). Administeredby a mentalhealth professional. Plusinformant interview andinspection of medical records.

Lastmonth

Belief of being persecuted, harassed, orunfairly treated that did not reach delusionalproportions was classified as paranoidideation 6.9%Persecutory delusion 3.5%

King's County,Brooklyn study.Cohen et al. (2004)

1027 adults (aged 55+)without cognitiveimpairment in Brooklyn,N.Y., USA. Four ethnicgroups sampled.

Paranoid sub-scale of theSCL-90 (Derogatis, Lipman,& Covi, 1973).Self-report questionnaire.

Past week Paranoid ideation present in 13%Paranoid ideation was considered presentif the respondent endorsed three or moreitems. The items in the scale are:

Feeling that you are watched or talkedabout by others.

Having ideas or beliefs that others donot share

Others not giving you proper credit foryour achievementsFeeling that people will take advantage ofyou if you let themFeeling others are to blame for most ofyour troublesFeeling that most people cannot be trusted

Studies of selected non-clinical samplesColumbia University

Study Olfson et al.(2002)

1005 adults (aged18–70) attendinga general medicinepractice in northernManhattan, N.Y., USA.

Mini InternationalNeuropsychiatricInterview (Sheehan et al.,1998). Not administeredby a mental healthprofessional.

Currentlypresent

Belief that others were spying on orfollowing them 10.6%Belief that people were plotting or tryingto poison them 6.9%Delusion of reference 4.7%Belief that people were secretly testingor experimenting on them 4.6%

Aquitaine SentinelNetwork studyVerdoux et al. (1998)

462 adults (18+ years)without psychiatricdisorder attendinggeneral medicinepractices inSouthwest France

Peters et al. DelusionsInventory (PDI) (Peterset al., 1999). Self-reportquestionnaire.

Lifetime Do you ever feel as if you are beingpersecuted in some way? 25.5%Do you ever feel there is a conspiracyagainst you? 10.4%

Paranoia surveyFreeman, Garety,Bebbington, Smithet al. (2005)

1202 universitystudents (ages 16–61)in SoutheastEngland, UK

Paranoia Checklist.Self-report questionnaire.

Lastmonth

Percentages of sample experiencingparanoid thoughts at least weekly:There might be negative commentsbeing circulated about me 42%Bad things are being said about me behindmy back 30%People deliberately try to irritate me 27%I might be being observed or followed 19%People are trying to make me upset 12%Someone I know has bad intentions towardsme 12%I am under threat from others 10%I have a suspicion that someone has it in forme 8%Someone I don't know has bad intentionstowards me 8%People would harm me if given theopportunity 8%There is a possibility of a conspiracy againstme 5%



quasicontinuous, lying between dichotomous and continuous (Van Os & Verdoux, 2003). An important implication ifthe continuum perspective is correct is that researching non-clinical delusional ideation can inform the understanding ofclinical phenomena, just as studying anxious or depressive states can inform the understanding of emotional disorders.

On the basis of a review of 15 studies, Freeman (2006) concludes that there is clear evidence that the rate ofdelusional beliefs in the general population is higher than that of psychotic disorders (i.e. that delusions occur inindividuals with experiences that have not been diagnosed as psychosis). The frequency of delusional beliefs in non-clinical populations varies according to the content of the delusion studied and the characteristics of the samplepopulation (e.g. age structure, level of urbanicity). Approximately 1–3% of the non-clinical population have delusionsof a level of severity comparable to clinical cases of psychosis. A further 5–6% of the non-clinical population have adelusion of less severity. Although less severe, these beliefs are still associated with a range of social and emotionaldifficulties. A further 10–15% of the non-clinical population have fairly regular delusional ideation. For example, Jimvan Os and colleagues studied delusions in the large epidemiological Netherlands Mental Health Survey and IncidenceStudy (NEMESIS). In the sample, 2.1% received a DSM-III-R diagnosis of non-affective psychosis. However, agreater proportion had a ‘true’ psychiatrist-rated delusion (3.3%), or had a ‘clinically not relevant delusion’ (8.7%)defined as the person not being bothered by the belief and not seeking help for it. A separate group of people hadendorsed a delusion item but these beliefs were considered plausible or founded (3.8%).

Many studies do not differentiate between delusion sub-types, and therefore it is harder to estimate the prevalence ofpersecutory thinking in particular. In Table 3 studies that include details of the occurrence of paranoid thinking aredisplayed. A conservative estimate is that 10–15% of the general population regularly experience paranoid thoughts,though such figures hide marked differences in content and severity. It is also likely that the studies underestimate thetrue frequency of paranoid thoughts because large epidemiological studies from a psychiatric perspective are unlikelyto record more plausible fleeting everyday instances of paranoid thinking. Johns et al. (2004) report findings from aBritish survey of over eight thousand people. Individuals with probable psychosis were removed from the study results.The assessment of delusions was fairly rudimentary: there was no assessment of conviction, differentiation betweenreal or unfounded events, or consideration of clinical severity. However the results are still striking. 20% had thought inthe past year that people were against them at times, and 10% felt people had deliberately acted to harm them. The leastplausible paranoid item, fears of a plot, was endorsed by 1.5% of this non-clinical population. So although this studydoes not provide robust data on the presence of delusional beliefs, it does indicate that thoughts of a paranoid nature arecommon in the non-clinical population. Interestingly, there is evidence from more elaborate epidemiological researchthat the distribution of paranoid thinking in the general population is continuous and that odder, less plausible paranoidthoughts build upon commoner, more plausible ones, indicating a hierarchical structure to paranoia (Freeman, Garety,Bebbington, Smith et al., 2005) (see Fig. 1). It is clinically noteworthy that a number of studies have found delusions inthe general population to be associated with distress and significant impairment in work, family and social functioning(e.g. Olfson et al., 2002).

The prevalence figures indicate that there is a need for literature on paranoid thinking that is aimed at the generalpopulation and is not focussed on severe mental illness (Freeman, Freeman & Garety, 2006). They are also consistentwith the idea of paranoid thoughts being an appropriate strategy that can, in particular circumstances, becomeexcessive, just like anxious thoughts. Consideration of the potentially hostile intentions of others can be a highlyintelligent and appropriate strategy to adopt. Walking down certain streets can feel threatening. Friends are not alwaysgood friends. As Francis Bacon (1612) noted: ‘What would men have? Do they think that those they employ and dealwith are Saints? Do they not think they will have their own ends, and be truer to themselves than to them?’Whether totrust or mistrust is a judgement that lies at the heart of social interactions and one that is prone to errors.

It has been seen that studies using traditional psychiatric assessments find that non-clinical populations experiencedelusions. Therefore it is reasonable to assume that they are indeed the same phenomena as seen in clinicalpopulations. There is also other evidence consistent with the idea that clinical and non-clinical experiences are linked.Non-clinical symptoms are associated with an increased likelihood of being diagnosed with a psychotic disorder(Eaton, Romanoski, Anthony, & Nestadt, 1991; Van Os, Hanssen, Bijl, & Ravelli, 2000). In particular, Van Os et al.(2000) found that plausible symptoms, secondary symptoms and non-clinically relevant symptoms were all verystrongly associated with the presence of clinical symptoms. Moreover, non-clinical and clinical experiences wereassociated with the same demographic and clinical risk factors (e.g. urban dwelling, living alone, depression). Theauthors view this as evidence of ‘aetiological continuity’ (seeMyin-Germeys, Krabbendam, & van Os, 2003). There isalso important evidence that non-clinical symptoms are predictive of the later development of psychosis (Chapman,

Fig. 1. The paranoia hierarchy.


Chapman, Kwapil, Eckbald, & Zinser, 1994; Poulton et al., 2000). The evidence is substantial enough to conclude thatstudying non-clinical paranoid experiences will inform the understanding of clinically severe persecutory delusions.

Finally, it should be highlighted that, while it has been established that paranoid thinking is a significant topic, there isconsiderable work to be done on its epidemiological study. Consideration needs to be given to the multi-dimensionalnature of the experiences, using assessments that separate the occurrence of such thinking from levels of belief convictionin the thought and associated distress. Just as importantly, greater consideration needs to be given to the content of thethoughts assessed. Persecutory thinking differs greatly in the nature of the threat and the identity of the persecutors. It hasalso been shown that specific aspects of the content of paranoid thinking (e.g. the power of the persecutor, the awfulnessof the threat) are associated with distress (Boyd & Gumley, in press; Chisholm, Freeman, & Cooke, 2006; Birchwood,Meaden, Trower, Gilbert, & Plaistow, 2000; Freeman et al., 2001; Green et al., 2006). Prevalence by content will differand there could be important differences in the detailed content of delusional ideation between clinical and non-clinicalgroups. This level of epidemiological scrutiny of paranoid thinking has not been carried out.

4. Psychological processes and persecutory thinking

Can the widespread experience of unfounded paranoid thoughts be explained psychologically? The focus will be onpsychological processes that have been empirically investigated in relation to persecutory ideation. Some of thepsychological processes (e.g. jumping to conclusions) have more often been investigated in relation to delusions ingeneral, which is a clear weakness for the review. Principal components analysis indicates that sub-types such asparanoia and grandiosity/fantastic delusions may have a degree of independence (Vázquez-Barquero, lastra, Nuñez,Castanedo, & Dunn, 1996) suggesting that there may be non-shared causes, although research on differential causes ofdelusion sub-types is yet to be carried out. A related methodological point is that most studies do not control for thecommon co-occurrence of symptoms found in clinical settings (Maric et al., 2004) so that spurious associations withparanoia might be found.


5. Anomalous experiences

‘the delusional belief is not being held “in the face of evidence normally sufficient to destroy it,” but is being heldbecause of evidence powerful enough to support it’ (Maher, 1974)

The American psychologist Brendan Maher (1974, 1988, 2003) emphasises that delusional ideas spring fromunusual internal experiences. The argument, simply put, is that odd experiences lead to odd ideas. This is consistentwith findings that many people with psychosis have clear anomalous experiences such as hallucinations, thoughtinsertion, and replacement of will, and also a range of more subtle perceptual and attentional alterations in experience(e.g. McGhie & Chapman, 1961) and, often, periods of arousal (e.g. Docherty, Van Kammen, Siris, & Marder, 1978;Hemsley, 1994). For instance, Bunney et al. (1999) found that 67 people with schizophrenia reported significantlymore perceptual anomalies, particularly in the auditory and visual modalities, than non-clinical controls. Patient reportsincluded: ‘Things are louder than normal: the TV is louder; other peoples' conversations seem louder,’ ‘Sometimes itseems like everything is coming in, like my brain is a radar for sounds,’ ‘Things in the corner of my eyes often catch myattention. I feel like I see everything at once.’ Kapur (2003) has highlighted the importance of aberrant feelings ofsalience in delusion formation, which is particularly of note since in this account the abnormal experience itselfconcerns processes of meaning ascription.

Odd internal experiences are clearly present in psychosis, but are they connected with delusions? There are anumber of strands of evidence – from patient reports, investigation of delusions and hallucinations over time, andexamination of the anomalous experiences of hearing impairment and illicit drug use – concerning this question.Asking individuals with delusions directly about their experiences using a structured interview finds, in two out of threestudies, that internal feelings and experiences are more often cited as evidence for the beliefs than external events(Buchanan et al., 1993; Freeman et al., 2004; Garety & Hemsley, 1994). In a study of 100 people with delusions, overhalf of whom had persecutory beliefs, it was found that non-delusional alternative explanations for the evidence takenfor the beliefs were uncommon (Freeman et al., 2004). Internal anomalous experiences were least likely to have analternative explanation, consistent with the anomalous experiences account; in part, individuals may explain puzzlingand confusing anomalous experiences delusionally because they have no alternative explanations to turn to.

Individuals in the non-clinical population also have anomalies of experience, such as hallucinations, and these havebeen found to be associatedwith delusional ideas (Bell, Halligan,&Ellis, 2006; Freeman et al., 2005a;VanOs et al., 2000).Krabbendam et al. (2004) used longitudinal data from the NEMESIS general population study to show a link betweenhallucinations and delusions. They found that the risk of developing psychosis is significantly increased if delusionalideation develops after hallucinatory experience, but not if hallucinatory experience occurs after delusional ideation. Theauthors conclude that their data are consistent withMaher's account in that delusional appraisal of anomalous experiencesis important in the development of clinical experiences.

Maher highlights how hearing impairments, conceived as an anomalous experience, can lead to paranoid thoughts.In older adults there is some evidence of associations of paranoia and hearing difficulties (Christenson & Blazer, 1984;Cooper & Curry, 1976), although this is not always found (Cohen, Magai, Yaffee, & Walcott-Brown, 2004; Östling &Skoog, 2002). In the NEMESIS general population study, hearing impairment was predictive of the presence ofpositive symptoms of psychosis 3 years later (Thewissen et al., 2005). Most intriguing perhaps is evidence from thefirst experimental manipulation study of paranoia. Zimbardo et al. (1981) studied 18 highly hypnotisable students. Allwere hypnotised; twelve had partial hearing impairment induced, with half being made aware of the source of theimpairment, and the remainder had an unrelated posthypnotic suggestion. Individuals who were unaware of theirhearing impairment had higher levels of paranoid ideation in a later social interaction compared with the other twogroups. This is clearly supportive of the anomalous experiences account of delusions.

Receivingmore contemporary interest has been the role of illicit drugs and psychosis (e.g. Murray, Grech, Phillips, &Johnsons, 2003). Two studies indicate that anomalies of experience caused by street drugs may be associated withdelusional ideas. D'Souza et al. (2004) showed in a double-blind randomised placebo controlled study involving 22 non-clinical individuals that the principal active ingredient in cannabis can cause transient increases in positive symptoms ofpsychosis and perceptual alterations (distorted time perception, external perception, feelings of unreality, and alteredbody perception). Participant experiences in this study included ‘I thought you were all trying to trick me by changingthe rules of the tests to make me fail,’ ‘I thought you could read mymind, that's why I didn't answer,’ ‘My thoughts werefragmented…the past present and future all seemed to be happening at once,’ ‘I thought I could hear the dripping of the


i.v. and it was louder than your voice.’ Using experience sampling methodology (repeated self-report assessment ofpatient experiences during the day) (Delespaul, 1995), Verdoux, Gindre, Sorbara, Tournier, and Swendsen (2003)showed that individuals with raised levels of non-clinical delusional or hallucinatory experience were more likely tohave unusual sensorial or perceptual experiences after smoking cannabis (i.e. there is an interaction between psychosisvulnerability and cannabis use). However these studies do not test whether drug-induced anomalies of experience lead todelusional ideas.

The anomalous experiences account is a difficult and under-researched area of study. Clearly, anomalies ofexperience are frequently found in individuals with delusions but the nature of their relationship remains to be testedconvincingly. It is the least researched of the areas covered in this review and the literature is somewhat fragmented andlacking in replicated findings. This is surprising since it is a very plausible route to delusional ideas, becauseindividuals often rely on feelings to guide judgements. However the lack of sustained attention is also understandable.Internal anomalous experiences are difficult to detect since it is partly the nature of the problem that they gounrecognised by the experiencer who forms delusional ideas. And an absence of good experimental measures of theprocesses underlying the anomalies means that self-report remains the main research strategy. There are also conceptualand methodological problems in trying to disentangle perceptions from interpretations. And as has been pointed out bymany authors, the anomalous experiences account cannot provide a complete answer to delusion formation. Manypeople have unusual experiences and do not get delusions. But this argument should not detract from the idea that thenature of some internal experiences may particularly lead to unlikely explanations.

6. Affective processes

‘it is perhaps worthy of notice that the various directions, which the delusions take in paranoia, correspond ingeneral to the common fears and hopes of the normal human being. They, therefore, appear in a certain manner asthe morbidly transformed expression of the natural emotions of the human heart.’ Kraepelin (1921)

The distinguishing of psychotic and affective disorders is one of the main boundaries in diagnostic classificationsystems. It is therefore intriguing that psychosis researchers have started to pay attention to the role of affectiveprocesses in delusional experience (Birchwood, 2003; Freeman & Garety, 2003). Some researchers have focussed onanxiety, others on depression, schemas and self-esteem, though clearly there is overlap between all these concepts. Allthe main studies of relevance concern persecutory ideation directly.

6.1. Anxiety

Paranoia concerns fear. A number of studies by Freeman and colleagues in both clinical and non-clinicalpopulations have stemmed from their observation that persecutory and anxious thoughts both concern the anticipationof threat; fears of physical, social or psychological harm are apparent both in anxious thoughts (e.g. Eysenck & vanBerkum, 1992; Wells, 1994) and in persecutory thoughts (Freeman & Garety, 2000; Freeman et al., 2001). It is arguedthat anxiety helps create thoughts of a paranoid content, and that anxiety-related processes contribute to themaintenance and distress associated with the experience.

At present the evidence for a link between anxiety and paranoia is reasonably strong. Anxiety has repeatedly been found tobe associatedwith paranoid thoughts (Freeman et al., 2005a; Fowler et al., 2006; Johns et al., 2004;Martin&Penn, 2001) andpersecutory delusions (Freeman & Garety, 1999; Huppert & Smith, 2005; Naeem, Kingdon, & Turkington, 2006; Startup,Freeman, Garety, in press). Better evidence for the role of anxiety in the development of paranoid thoughts is that anxiety ispredictive of the occurrence of paranoid thoughts (Freeman et al., 2003, 2005b) and of the persistence of persecutorydelusions (Startup et al., in press). Moreover, it has been shown in non-clinical groups that paranoid thoughts build uponcommon interpersonal anxieties and worries (Freeman, Garety, Bebbington, Slater et al., 2005; Freeman, Slater, et al., 2003;Freeman, Garety, Bebbington, & Smith et al., 2005c). The most common type of suspiciousness is that of a social anxiety orinterpersonal worry theme; ideas of reference build upon these sensitivities; persecutory thoughts are closely associated withthe attributions of significance; and as the severity of the threatened harm increases, the less common is the thought. Theimplication is that severe paranoia may build upon common emotional concerns.More broadly, the hypotheses are consistentwith innovative work showing greater stress sensitivity in people with psychosis (Myin-Germeys, Delespaul, & van Os,2005). Intriguingly, Schulze et al. (2005) report a similar genetic marker for persecutory delusions and anxiety.


Paranoid thinking and anxiety-related processes have been linked. Initial evidence indicates that almost two-thirdsof individuals with persecutory delusions have a worry thinking style (even about matters unrelated to paranoia)(Freeman & Garety, 1999; Startup et al., in press). Worry in individuals with persecutory delusions is associated withhigher levels of distress and with delusion persistence. Other anxiety-related processes are also apparent in people withpersecutory delusions. An example is safety behaviours (Freeman et al., 2001, 2007). Individuals who feel threatenedoften carry out actions designed to prevent their feared catastrophe from occurring; this has been termed ‘safetybehaviour’ (Salkovskis, 1991). When the perceived threat is a misperception, such as in anxiety disorders and paranoia,there are important consequences. Individuals fail to attribute the absence of catastrophe to the incorrectness of theirthreat beliefs. Rather, they believe that the threat was averted only by their safety behaviours (e.g. ‘The reason I wasn'tattacked was because I left the street in time and made it back home’). Threat beliefs are likely to persist partly due tothis failure to obtain and process disconfirmatory evidence. Freeman et al. (2007) found that 96 out of 100 patients withpersecutory delusions had used safety behaviours in the past month.

In the course of their work, Freeman and colleagues have collaborated with computer scientists to develop, usingvirtual reality (VR), the first method to study persecutory ideation in the laboratory (Freeman et al., 2003, 2005b). Withvirtual reality the environment is controlled; individuals can therefore enter an identical situation, and so appraisals forthe same event can be assessed and psychological factors associated with particular appraisals identified. In applying thismethod to the study of persecutory ideation, virtual characters (‘avatars’) in a virtual environment can be programmed toexhibit only behaviour that most people would assess as neutral. Individuals' appraisals of the avatars can then beassessed, and the psychological factors that lead some individuals to have (clearly unfounded) persecutory thoughtsdetermined. In the studies, most people found that the virtual library environment used neutral or even positive. Howeverabout a third had persecutory thoughts about the avatars. In both published studies, anxiety and interpersonal sensitivitywere predictors of unfounded persecutory ideation in virtual reality. However, these authors also note the important taskof identifying differential predictors of anxiety and paranoia. They carried out the first study investigating this issue bynot only measuring persecutory thoughts in VR but by also assessing social anxiety thoughts about the avatars.Interestingly, the prediction of persecutory ideation and social anxiety in virtual reality shared many of the same factors –and this is unsurprising given the similarities in their threat content – but what sets apart the prediction of persecutoryideation from that of social anxietywas the presence of predisposition to hallucinatory experience. The findings support theview that emotional disturbance can lead to social anxiety but that the addition of anomalous experiences such ashallucinations makes persecutory ideation more likely.

6.2. Depression, self-esteem and schemas

The issue of the relationship between paranoia and emotion is more controversial when it concerns depression andself-esteem. Richard Bentall, a leading pioneer of the research field, argues that persecutory delusions are a defenseagainst negative affective processes (Bentall et al., 1994; Bentall et al., 2001). In contrast, Freeman and colleagues putforward the view that persecutory delusions are a direct reflection of emotional concerns (Freeman et al., 2002;Freeman et al., 2004; Freeman et al., 2005c). Trower and Chadwick (1995) argue that there are two quite distinct formsof paranoia, one of which is a defense (Poor Me paranoia) and the other of which is a direct reflection of extremenegative emotion (Bad Me paranoia). It is worth noting that some delusion-as-defense theories focus on the avoidanceof negative self-esteem and some focus on the avoidance of depression, but, nonetheless, negative self-esteem anddepression are typically found to correlate in studies of persecutory delusions (Chadwick, Trower, Juusti-Butler, &Maguire, 2005; Drake et al., 2004; Freeman et al., 1998, 2001; Lyon, Kaney, & Bentall, 1994).

A simplified view would be that if delusions are a defense then self-esteem should be normal but if paranoia buildson negative views of the self then self-esteem should be low. Bentall et al. (2001) consider the self-esteem data andargue that there are very mixed findings concerning levels of self-esteem in paranoia, with some studies finding lowself-esteem and some preserved self-esteem. Their explanation for this is that there is instability in self-esteem in peoplewith paranoia, and that these individuals are locked into a struggle to defend against negative emotion, sometimeswinning, sometimes losing (which clearly makes the theory harder to test). There is, however, perhaps a clearer, lesscomplicated picture apparent in the self-esteem and paranoia data, which will now be described.

There are actually few studies that simply look at current levels of self-esteem in individuals with currentpersecutory delusions compared with a matched non-clinical control group. And the number of patients in thesestudies is small and most likely comprises unrepresentative samples. Studies of paranoia in the non-clinical


population provide much better information on the issue because they include a much larger number of participants,have a greater range in paranoia scores compared to clinical groups because of the dimensional approach adopted,and avoid the complications of the effects of being a patient with psychosis on self-esteem and depression (e.g.receiving a diagnosis, compulsory treatment, medication, unemployment, stigma). The findings in non-clinicalpopulations are clear: paranoia is repeatedly found to correlate with lower self-esteem and higher depression (Ellett,Lopes, & Chadwick, 2003; Freeman et al., 2005a; Fowler et al., 2006; Johns et al., 2004; Martin & Penn, 2001;McKay, Langdon, & Colheart, 2005). For instance, in a representative population survey of over eight thousandpeople in the UK, Johns et al. (2004) found that paranoid thinking was associated with symptoms of anxiety anddepression, victimisation experiences, and recent stressful life events. The finding of an association of lowered self-esteem and paranoia is not unique to non-clinical groups. Drake et al. (2004) in a study of approximately twohundred first episode patients found paranoia to be associated with depression and lower self-esteem at several timepoints over 18 months. Furthermore, this study fits within a larger literature indicating an association of affectiveproblems with the positive symptoms of psychosis (e.g. Freeman, 2006; Guillem et al., 2005; Norman & Malla,1994; Sax et al., 1996) and evidence that low self-esteem and anxiety predict the later development of positivesymptoms of psychosis (Krabbendam et al., 2002).

So what do these findings indicate? Unless self-esteem is considered as the only cause of paranoia then there isno reason to expect everyone with paranoia to have the same level of self-esteem (it might even be considered anodd finding). But what is clear from the self-esteem data is that there is in general an association of paranoia withlowered self-esteem and depression. The distribution of self-esteem and mood is skewed towards the negative inparanoia, which would not be expected if persecutory thoughts serve as a defense. Many individuals with paranoiahave lowered self-esteem but some do not. But of course there is the difficulty of determining the causal direction ofthe association. It is entirely plausible that having paranoid thoughts would lower mood and self-esteem.Experimental studies examining causal issues are needed. It is most likely that there is a circular relationship, withlow self-esteem and depression being one of a number of vulnerability factors for paranoia, which then decreasesself-esteem and increases depression further.

But the debate about global self-esteem and paranoia may obscure the important point. Self-esteem may not bethe key concept when considering paranoia; rather it is specific negative beliefs about the self and others that areimportant (Chadwick et al., 2005; Freeman et al., 2002; Fowler, 2000; Fowler et al., 2006; Garety et al., 2001). Inboth non-clinical (Freeman et al., 2003, 2005b) and clinical studies (Fowler et al., 2006; Smith et al., 2006),paranoia has been found to be associated with negative self-beliefs and sensitivities. In what is likely to prove a keypaper in the area, David Fowler et al. (2006) found that in a non-clinical population of over seven hundred studentsparanoia was associated with negative beliefs about the self, negative beliefs about others, less positive beliefsabout others, and anxiety. Self-esteem as traditionally measured was not as good a predictor of paranoia and, unlikeschematic beliefs, did not discriminate between the non-clinical group and a group of two hundred and fifty patientswith psychosis.

Of course, negative schematic beliefs are related to self-esteem, but they are not exactly the same (Fowler et al.,2006). When specific negative beliefs are considered, and the exact content may vary in the individual case, thenlinks with paranoia are more likely to be found. This fits with Christine Barrowclough et al. (2003) arguing thatself-esteem needs to be assessed in a very detailed interview to find links with symptoms of psychosis. However,just as with depression and schema, there is a clear problem in establishing the direction of causal effects in therelationship between paranoia and schematic beliefs. It is likely to be a circular effect.

The parsimonious explanation of associations of negative self beliefs, lowered self-esteem and depression withclinical and non-clinical paranoia is that they are directly associated, without the need to evoke defensive processes.But a stricter test of defense theories of paranoia would be whether covert self-concept is lower than overt presentations(i.e. there is discrepancy between core beliefs about the self and those in conscious awareness). Clearly it is amethodological difficulty to penetrate hypothesised defenses and a negative finding could always be interpreted as afailure of methodology rather than theory. It has been argued that the emotional Stroop task is currently the mostplausible defense-penetrating task (Garety & Freeman, 1999; Smith, Freeman, & Kuipers, 2005). The delusion-as-defense model would predict biases towards negative self-concept words using the Stroop but for overt self-esteem tobe comparable to controls. However, even the first step of showing biases towards depressive words has not beenshown in some studies (Bentall & Kaney, 1989; Fear, Sharp, & Healy, 1996), and discrepancy with overt self-esteemusing this method has not been demonstrated. Evidence for a discrepancy has rested on one particular method using


two different measures of attributions (Lyon et al., 1994) but there have been failures to replicate with this particularmethodology (Kristev, Jackson, & Maude, 1999; Martin & Penn, 2002; McKay et al., 2005; Peters & Garety, 2006).Moreover, it is of methodological note that in none of the attribution studies has the crucial test of discrepancy betweenattribution measures at an individual level been tested statistically. Instead the studies have simply looked at patterns ofresults at a group level for each measure. Even in grandiose delusions, where the delusion might be more likely toprotect the self, evidence of discrepancy between overt and covert self-esteem is lacking (Smith et al., 2005).

Can it simply be that there are two distinct sub-groups of paranoia as suggested by Trower and Chadwick(1995)? No systematic empirical tests have been made of this interesting theoretical account; most obviously, therehas been no comparison of overt and covert self-esteem in Poor Me and Bad Me paranoia groups. There are onlytwo empirical lines of evidence directly related to the theory. Unsurprisingly, Bad Me paranoia is associated withgreater depression and negative self-esteem than Poor Me paranoia (Chadwick et al., 2005; Freeman et al., 2001).But it also seems that cases of Poor Me paranoia may be uncommon; Fornells-Ambrojo and Garety (2005) foundonly three cases of Bad Me paranoia in 40 individuals with early episode psychosis and paranoia. An alternativeaccount of the current evidence is that the concept of deservedness is an important (dimensional) aspect of thecontent of paranoia associated with distress, but not an indicator of discrete categories with opposite causes.

In summary, when understanding paranoia it may be better to think in terms of specific schematic beliefs rather thanglobal self-esteem. Paranoia may well often build on negative ideas about the self, others and the world. If the measureis appropriate then paranoia is often associated with self-concept concerns, which are in general apparent in people withparanoid thoughts. Schematic concerns may provide content to paranoid thoughts but perhaps not affect conviction inthe thoughts to a large degree. If negative self-esteem is present then it may be particularly associated with the distressof paranoid experience. Overall there is now considerable evidence of affect and related processes having a direct, non-defensive, role in the development of paranoid thoughts. Anxiety may be especially important in paranoid thoughts.However, causal tests of hypothesised factors are now needed. It is also of note that psychological factors such as socialrank, power differentials and submissive behaviours have been studied in pioneering studies of the distress of auditoryhallucinations but are yet to be fully applied to paranoia and may be another important element in understanding theexperience (Freeman et al., 2005c; Gilbert, Boxall, Cheung, & Irons, 2005).

7. Reasoning

‘The degree of paranoia stifled my ability to live and think freely. False suspicions impeded my progress in goingforward. Once I began to question, my suspicions could not be verified. Once I acknowledged that there were holes ofuncertainty, I began to think that some of my thoughts might be delusional even though they had the appearance oftruth and believability. As each day passed and I wasn't killed, I dug deeper at my own scared pace.’Chapman (2002).

Robert Chapman (2002) describes his determined recovery from delusions using a self-devised four-step strategy ofdoubting paranoid beliefs, recognising and identifying delusional thoughts, processing disconfirmatory evidence, andconsidering alternative explanations. His approach is based upon testing delusional beliefs using reasoning strategies.If delusions are incorrect – or perhaps, more importantly, uncorrected – beliefs, then judgemental or reasoningprocesses are inherently implicated in their cause. A number of researchers have therefore tried to identify biases ordeficits in reasoning in individuals with paranoia.

7.1. Jumping to conclusions

Reasoning had long been assumed to be awry in people with delusions, but empirical evidence for this view had notbeen forthcoming. In innovative work from the late 1980s onwards, Philippa Garety and colleagues provide empiricalevidence that individuals with delusions ‘jump to conclusions’ (JTC). In an experimental probabilistic reasoning taskindividuals are required to decide from which of two hidden jars coloured beads are being drawn. The jars both containbeads of two different colours but the proportion of beads of each colour in the jars is reversed. Typically, one jar willcontain 85 black beads and 15 yellow beads and the other jar will contain 85 yellow beads and 15 black beads. It hasbeen found that individuals with delusions request fewer pieces of information (i.e. to see fewer beads drawn from thejar) before making a decision compared with non-clinical controls (see review by Garety and Freeman, 1999). Such abias in data gathering is hypothesised to lead to the rapid acceptance of beliefs even if there is limited evidence to


support them, and hence be a factor in delusion development and maintenance. Probabilistic reasoning has rarely beenstudied in relation to delusion sub-type. In Table 4 studies of probabilistic reasoning are summarised but with anemphasis on the presence of persecutory delusions in the samples. Only studies that allow the participants to gather datafreely are reported.

Remarkably, in all ten clinical studies where individuals with delusions are compared with non-clinical controls onthe number of draws to decision in probabilistic reasoning tasks, data gathering is hastier in the delusion group. Suchreplication of a finding is rare in psychosis research and is firm evidence for the presence of a JTC bias in individualswith delusions. One half to two-thirds of individuals with delusions jump to conclusions (defined as making a decisionafter two or fewer beads). A study of one hundred individuals with delusions indicates that JTC may be particularlyassociated with delusional conviction (Garety et al., 2005). But is the bias apparent in people with persecutorydelusions? This is much less clearly shown by the studies. In only seven studies is information on the presence ofpersecutory delusions available. Individuals with persecutory delusions were the focus of only one study (Startup,2004) and were present in at least half the participants in the other six studies. The limited conclusion that can be madeat present on this information is that JTC is often present in people with persecutory delusions. However, there havebeen no tests of specific associations with delusion sub-types. In most cases individuals with persecutory delusionswould have had other delusion beliefs and therefore whether JTC is more strongly associated with another delusionsub-type such as grandiose delusions remains to be investigated.

The evidence base on JTC concerns individuals with current delusions. However, there are two intriguing recentstudies of JTC in groups that are not currently deluded. Broome et al. (in press; pers. com.) found evidence that hastydata gathering is present in a group identified as at risk of developing psychosis, indicating that the bias may be presentbefore delusions occur, although it was only in the more difficult versions of the reasoning task that JTC was apparent.JTC may be a cause of delusions. In an important study, Van Dael et al. (2006) studied JTC in individuals withpsychosis and their relatives, and individuals in the general population high or low in non-clinical psychotic symptoms(i.e four groups differing in levels of delusional ideation and vulnerability to psychosis). Hasty data gathering wasassociated with both delusional ideation and psychosis liability. As the authors argue, JTC may be both partly a traitfactor reflecting liability for psychosis and partly a state factor as it covaries with level of delusional ideation. In otherwords, JTC could contribute to both delusion formation and maintenance. Consistent with this work, two studies havefound JTC in individuals whose delusions have remitted (Mortimer et al., 1996; Moritz and Woodward, 2005),although one study did not (Peters & Garety, 2006). Colbert and Peters (2002) found evidence of JTC in non-clinicalindividuals with high delusional ideation compared with individuals with low clinical delusional ideation, but this wasnot replicated by Van Dael et al. (2006). Furthermore, in the only non-clinical study to examine an association of JTCand paranoid thinking, there was no evidence for such a link (Freeman et al., 2005b). Biases in reasoning may be muchmore subtle outside of acute delusional states.

In addition to the exact relationship of JTC to the development of delusions, the cause of hasty data gathering itselfremains to be determined. There have been a number of speculations: Dudley and Over (2003) note the need toconsider the goal of reasoning; Moritz and Woodward (2004) raise the issue of the level of the threshold at which anexplanation is accepted; the belief confirmation bias (Freeman, Garety, McGuire, & Kuipers, 2005) or a bias againstdisconfirmatory evidence (Moritz & Woodward, 2006b) may be related to JTC; and data gathering is likely to beinfluenced by the availability of alternative explanations for experiences (Freeman et al., 2004). Previous suggestionsthat JTC reflects a generalised need for closure have been discounted however (Freeman, Garety, Kuipers, Colbert,Jolley et al., 2006).

Biases in data gathering will plausibly affect belief formation and maintenance, enabling the rapid acceptance ofimplausible explanations. However, it should also be noted that a JTC bias might distort the evidence. For example,Moritz and Woodward (2006a) suggest that JTC may lead to acceptance of false memories or knowledge corruption,while misattribution biases hypothesised to be important in the occurrence of hallucinations have been found to beassociated with delusional ideation (e.g. Johns et al., 2006; Allen, Freeman, Johns, & McGuire, 2006). The complexityis that reasoning biases may contribute to the anomalies of experiences that are taken as the evidence for delusionalbeliefs.

Future studies will benefit from not considering data gathering in isolation. More detailed experimental work isneeded on the interaction of the production of potential explanations, data gathering, the processing of confirmatoryand disconfirmatory reasoning, the acceptance of explanations, and how beliefs change. Furthermore, how these aremodified by current goals, emotional state, and interactions with others needs to be examined. Causal studies of

Table 4Jumping to conclusions (as assessed by the probabilistic reasoning task)

Study Groups of participants Proportion delusion groupwith persecutory beliefs

Task Jumping to conclusionsas assessed by draws todecision (in delusiongroups compared withnon-clinical controls)

Comments

Delusion studiesHuq, Garety, and

Hemsley (1989)15 delusions ? 85:15 beads ratio ✓10 psychiatric control15 non-clinical controls

Garety et al. (1991) 27 delusions ? 85:15 beads ration ✓ 55% of the delusion group jumped to conclusions (twobeads or fewer). 11% of the non-delusion participantsshowed JTC.

14 anxious13 non-clinical control

Mortimer et al. (1996) 43 patients withschizophrenia

? 85:15 beads ratio The study did not include a control group and thereforeit is unknown whether the clinical group shows hastydata gathering in relation to non-clinical controls.It is not known how many of the participants haddelusions.42% of the sample were reported as jumping toconclusions defined as deciding after one bead has beendrawn.

Dudley et al. (1997a) 15 delusions 73% (Dudley, pers. com). 85:15 and 60:40 beadsratios

✓ The delusion group requested fewer beads in bothversions of the beads task.15 depression

15 non-clinical controlsDudley et al. (1997b) 15 delusions of

persecution or grandeur73% (Dudley, pers. com) 60:40 neutral word stimuli

ratio✓ The delusion group requested fewer words in both

versions of the task. Emotionally salient stimuli reduceddata gathering in all three groups.16 depression 60:40 emotionally

salient word stimuliratio

15 non-clinical controls

Fear and Healy (1997) 30 delusions ? 85:15 beads ratio ✓ 73% of the delusion group showed jumping toconclusions as defined by deciding after one bead. 20%of the non-clinical control group jumped to conclusions.

16 obsessional anddelusional features29 obsessive-compulsivedisorder30 non-clinical controls

Conway et al. (2002) 10 delusions 50% 85:15 beads ratio ✓ The beads task was administered four times and averagescores used. 70% of the delusion group and 10% of thecontrol group jumped to conclusions defined as adecision after two beads or fewer.


Startup (2004) 28 Persecutory delusions 100% 60:40 beads ratio ✓ 50% of the delusion group showed jumping toconclusions defined as deciding after two beads orfewer. 10% of the control group showed JTC.

30 Non-clinicalparticipants

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Moritz and Woodward(2005)

17 delusions 100% 90:10 beads ratio ✓ Defining JTC as making a decision after two or fewerbeads, 65% of the delusion group, 43% of the nocurrent delusions schizophrenia group, 21% of thepsychiatric controls and 6% of the non-clinicalcontrols showed JTC.

14 schizophrenia and nocurrent delusions

All participants hadat least mild paranoidideation/suspiciousnessas assessed with theBrief PsychiatricRating Scale item 11(Moritz, pers. Comm.).

28 psychiatric controls17 non-clinicalcontrols

Garety et al. (2005) 100 delusions 70% (SAPS N2) 85:15, 60:40 beadsratios. 60:40emotionally salientword stimuli taskalso used

A non-clinical control group was not included in thisstudy. With JTC defined as making a decision aftertwo beads or fewer:

53% showed JTC on the 85:15 tasks41% showed JTC on the 60:40 task37% showed JTC on the emotionally salient

words task.Peters and Garety(2006)

23 delusions 61% 85:15 beads ratio ✓ It is also of note that in this study the groups werefollowed up over time. Individuals with delusionsthat had remitted did not differ from non-clinicalcontrols in data gathering.

22 psychiatric controls36 non-clinical controls

Van Dael et al.(2006)

40 individuals withschizophrenia

? 85:15 ✓ Jumping to conclusions (defined as deciding after onebead) was found in 32.5% of the individuals withschizophrenia; 25% of the relative group; 14.6% of thenon-clinical high symptom group; and 11.3% of thecontrol group.

40 first degreenonpsychotic relatives41 non-clinical individualswith psychoticexperiences53 non-clinical controls JTC was associated with delusional ideation and

psychosis liability across the groups.Broome et al. (in press;pers. com.)

31 at risk of psychosis 85:15, 60:40 and44:28:28 beads ratios

✓ The ‘at risk’ group showed hasty data gathering on thetwo more difficult beads ratio tasks(but not the 85:15 task).


Draws to decision were correlated with delusionalconviction in all participants.

Non-clinical studiesColbert and Peters(2002)

17 non-clinical individualshigh in delusional ideation

85:15 beads ratio ✓

17 non-clinical individualslow in delusional ideation

Freeman, Garety,Bebbington, Slateret al. (2005)

30 non-clinical individuals Scorers across the full range ofnon-clinical paranoia

85:15 beads ratio X There was no evidence of jumping to conclusions beingassociated with paranoid thoughts in anexperimental situation.

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reasoning and delusional ideation are clearly indicated now. This work has relevance for the study of delusional beliefsbut also more generally for cognitive therapy approaches to problems where changes in beliefs are targeted.

7.2. Attributional style

The literature on attributional style developed by Richard Bentall and colleagues has been closely linked to thedelusion-as-defense theory, but attributional style need not be tied to such a theoretical framework; if a person tends toexplain events in terms of other people then this would be a plausible factor in the creation of paranoid thoughts,without evoking the further hypothesis that the explanation serves to defend the self-concept. This means that the keyissue is not whether individuals with delusions have a self-serving bias (i.e. differences in the types of attributions givenfor positive and negative events) but, given the negative content of paranoid thoughts, whether external attributions fornegative events are made. Snyder's (2006) account of his paranoid episode illustrates a strong bias to explain events ina particular way: ‘My concept of THEM grew and began to colour every experience I had. After a few months,everything that happened to me was somehow related to THEM, or was caused by THEM.When I started experiencingproblems with my home computer, I blamed THEM. When I got a parking ticket, it was THEIR influence with thepolice that got me into trouble. Every thought that I had was somehow associated with THEM.’

Most attribution studies have used either the Attributional Style Questionnaire (ASQ) (Peterson et al., 1982) or theInternal, Personal and Situational Attributions Questionnaire (IPSAQ) (Kinderman & Bentall, 1996a). The basic designof these questionnaires is similar. A hypothetical event is described (e.g. ‘You go on a date and it goes badly’) and theparticipant is asked to note a cause and then rate it for how much the cause is due to something about them or tosomething about other people or circumstances. The results of these studies are summarised in Table 5.

Three ASQ studies (Fear et al., 1996; Krstev et al., 1999; Lyon et al., 1994) show clear evidence of an externalising biasfor negative events in people with persecutory delusions compared with non-clinical controls and two ASQ studies find nodifferences between persecutory delusion and non-clinical control groups (Kinderman, Kaney, Morley, & Bentall, 1992;Martin & Penn, 2002). None of the four IPSAQ studies finds evidence of an externalising bias for negative events inpersecutory delusion groups compared with non-clinical controls (Kinderman & Bentall, 1996b; Martin & Penn, 2002;Randall, Corcoran, Day, & Bentall, 2003; McKay et al., 2005). In the first clinical study using the IPSAQ, Kinderman andBentall (1996b) found that, when external attributionsweremade, individualswith persecutory delusionsweremore likely tomake external–personal attributions compared to non-clinical controls (who were more likely to make external–situationalattributions). However, this has not been replicated in three further clinical studies (Martin & Penn, 2002; McKay et al.,2005; Randall et al., 2003). In studies of non-clinical paranoid ideation in student groups only one of three studies finds anassociation of paranoia and a personalising bias (Kinderman & Bentall, 1996a).

Overall, four out of nine studies using the two attribution measures indicate that there are differences betweenindividuals with persecutory delusions and non-clinical controls in attributions for negative events. Therefore, theempirical case for persecutory delusions being associated with an excessive externalising style for negative events isunconvincing at present. A large-scale study is needed, but it will be important to control for both grandiosity anddepression since there is evidence for their association with attributional style (e.g. Jolley et al., 2006). However, itshould be noted that the questionnaire assessments of attributional style used may limit the chances of finding evidenceof an externalising style. There are concerns over the psychometric properties of questionnaires such as the ASQ (e.g.Krstev et al., 1999) and anecdotal reports indicate that participants have difficulties completing the attributionquestionnaires. Perhaps most importantly, clinical experience indicates that the questionnaires do not assess the typesof events that delusional attributions concern. Delusions often concern ambiguous social events (e.g. the look on a face,the gesture of a person) and, as discussed earlier, confusing internal experiences. The ASQ was designed for depressionresearch and does not assess these sorts of experiences.

7.3. Theory of mind

Individuals with persecutory ideation are by definition sometimes misreading the intentions of other people.Therefore a candidate cause is the mechanism of determining others' mental states. Drawing upon established researchinto children's understanding of ‘folk psychology,’ and drawing a close analogy with autism, Frith (1992, 2004)proposes that symptoms of schizophrenia develop from newly acquired difficulties in a person's ‘theory of mind’ skills(ToM) (Premack & Woodruff, 1978). ToM refers to the ability to understand mental states (beliefs, desires, feelings,

Table 5Attributional style for negative events (assessed by the ASQ or IPSAQ)

Study Groups of participants Attributional measure Externalising bias fornegative events (indelusion group comparedwith non-clinical controls).

Comments

Clinical psychosis studiesKinderman et al. (1992) 23 persecutory delusions ASQ X From graphed data it appears from visual inspection that the

delusion group score comparably to the non-clinical group onattributions for negative events. The depressed group, however,makes more internal ratings for negative events.

21 psychiatric control28 non-clinical control

Candido and Romney (1990) 15 persecutory delusions ASQ ? This study did not include a non-clinical control group andtherefore the presence of an externalising bias in individuals withpersecutory delusions cannot be tested. In comparison withdepressed patients, individuals with persecutory delusions mademore externalising attributions for negative events, but this couldbe due to people with depression showing an internalising bias.

15 persecutory delusionsand depression

15 depression Attributions were associated with levels of depression and paranoia.Higher depression was associated with more internalising. Higherparanoia was associated with more externalising.

Lyon et al. (1994) 14 persecutory delusions ASQpf ✓ In this study a new parallel version of the ASQ was used.14 depression control group14 non-clinical control

Fear et al. (1996) 20 persecutory delusions ASQ ✓ The externalising style was present in both individuals withpersecutory delusions and individuals with non-persecutorydelusions (mainly grandiose).

9 non-persecutory delusions20 non-clinical controls

Sharp et al. (1997) 19 persecutory and/or grandiosedelusions (14 persecutory,5 grandiose)

ASQ ✓ Externalising specific to persecutory/grandiose group and not toother delusion sub-types.

12 somatic or jealousy delusions24 non-clinical controls

Krstev et al. (1999) 62 individuals with first episodepsychosis, but none held apersecutory delusion at thetime of testing

ASQpf X The parallel version of the ASQ developedby Lyon et al. (1994) was used.The authors did not include a non-clinicalcontrol group. They compared their results withother studies to argue that an excessiveexternalising bias for negative events is not apparent.Higher levels of depression were associated with moreinternalising, whilehigher levels of suspiciousness were associatedwith less internalising for negative events.

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Study Groups of participants Attributional measure Externalising bias fornegative events (indelusion group comparedwith non-clinical controls).

Comments

Clinical psychosis studiesJolley et al. (2006) 7 persecutory delusions ASQ ? The absence of a non-clinical control group prevents determination

of whether an externalising bias was present. However there weregroup differences in externalising for negative events. Individualswith persecutory and grandiose delusions were more likely toexternalise negative events than the persecutory delusions anddepression group and the non-persecutory delusions group. In thewhole sample, the presence of both grandiosity and persecutorydelusions was associated with externalising attributions fornegative events and not persecutory delusions or grandiosedelusions on their own.

23 persecutory delusionsand depression7 persecutory andgrandiose delusions

34 non-persecutorydelusions psychosis

Martin and Penn (2002) 15 persecutory delusions ASQ X Using two measures of attributions there was no evidence ofeither excessive externalising or personalising attributionsin individuals with persecutory delusions basedupon their self-report.

15 non-persecutory delusionsschizophrenia group(9 had no delusions)

IPSAQ X

16 non-clinical controlKinderman and Bentall(1996b)

20 persecutory delusions IPSAQ X The persecutory delusion group scored comparably to thenon-clinical group for whether an external attribution was madefor a negative event.

20 psychiatric control However, when an external attribution was made, the persecutorydelusion group was more likely to make a personalising attributionthan the non-clinical control group. The non-clinical controlgroup was more likely to make situational external attributionsthan the persecutory delusions group.

20 non-clinical Paranoia scale scores were not correlated with the tendency topersonalise external attributions.Depression scores were associated with internal but notpersonalising attributions.

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Randall et al. (2003) 19 persecutory delusions IPSAQ X There were no differences in internal, personal, or situationalattributions for negative events for the three groups as self-rated.14 persecutory delusions

in remission18 non-clinical control

McKay et al. (2005) Study 2 IPSAQ X The persecutory delusion group made more internal attributionsfor negative events than the control group (accounted forby levels of depression).

13 persecutory delusions

12 remitted persecutorydelusions group

All groups had comparable scores for level of personalisingattributions for negative events.

19 non-clinical controls The control group made more situational attributions for negativeevents than the persecutory delusion group (accounted forby levels of depression).

Langdon et al. (2006) 19 persecutory delusions IPSAQ ? The groups were not compared on the numbers of internalattributions for negative events. However, there were nosignificant differences inlevels of personalising of negative events between the three groups.

15 non-persecutory delusionschizophrenia group(nine had no delusions)21 non-clinical controls

Non-psychosis studiesKinderman and Bentall

(1996a)85 non-clinical students IPSAQ Higher levels of non-clinical paranoid ideation were associated with

making personalising external attributions.Depression was associated with making internal attributions.

Martin and Penn (2001) 193 non-clinical students IPSAQ Higher levels of non-clinical paranoid ideation were not associatedwith a personalising bias for negative events.

McKay et al. (2005) Study 1: 40 non-clinicalstudents

IPSAQ No association of persecutory ideation and attributional style was found.A drawback for interpretation of this study is that the authors use anunpublished novel measure of persecutory ideation.

Blackshaw et al. (2001) 25 individuals withAsperger syndrome

IPSAQ Individuals with Asperger syndrome had higher levelsof paranoia than the control group but did not differsignificantly in the presence of a personalisingbias for negative events.

18 non-clinical control group

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and intentions) in the self or others. Previously, Cameron (1959) observed that people vulnerable to paranoia are“unable to understand adequately the motivations, attitudes, and intentions of others.” Frith argues that delusions ofpersecution and reference arise from the person with schizophrenia knowing that people have mental states that cannotbe directly viewed, but making invalid attempts at inferring them. According to Frith, delusions of reference occurbecause a person with schizophrenia mistakenly labels an action as having an intention behind it. Persecutory delusionsarise because the person notices that other peoples' actions have become opaque and surmises that a conspiracy exists.

Frith's innovative research has led to a large literature in which tasks assessing different levels of ToM abilities havebeen used with people with schizophrenia. Indeed this is now the most researched psychological process and psychosis,and it could be argued that an association of ToM performance and paranoia has been more stringently tested than theother psychological factors reviewed. There is a consensus that ToM difficulties are apparent in people with a diagnosisof schizophrenia, and may be most severely present in individuals with negative symptoms and incoherent speech(Brüne, 2005; Garety & Freeman, 1999; Harrington, Langdon, Seigert, & McClure, 2005; Harrington, Siegert, &McClure, 2005; Sarfati, Hardy-Baylé, Besche, & Widlöcher, 1997). Indeed, this association with negative symptomsmay be expected from the neuropsychological literature; ToM tasks and executive functioning have been found to belinked in the developmental psychology literature (e.g. Hughes, 2002) and executive functioning difficulties have beenfound to be associated with negative symptoms and thought disorder but not the positive symptoms of psychosis (e.g.O'Leary et al., 2000). Difficulties with ToM may be a trait factor associated with liability to psychosis (Janssen,Krabbendam, Jolles, & van Os, 2003).

As Frith (2004) notes, however, the ToM findings for paranoia may be more equivocal. In Table 6 ToM studies arelisted that include a comparison of individuals with predominately paranoid symptoms and non-clinical controls, orthat examine correlations between positive symptoms and ToM performance.

It is clear that ToM problems do occur in people with predominately paranoid symptoms. In eight studies ToMperformance in people with paranoid symptoms is poorer relative to controls (Corcoran, Cahill, & Frith, 1997; Corcoran,Mercer, & Frith, 1995; Craig, Hatton, Craig, & Bentall, 2004; Frith & Corcoran, 1996; Harrington, Langdon, Siegert, &McClure, 2005; Langdon, Corner, McLaren, Ward, & Coltheart, 2006; Randall et al., 2003; Russell, Reynaud, Herba,Morris, & Corcoran, 2006). There is only one failure to replicate (Pickup & Frith, 2001). However, ToM problems are notnecessary for paranoid experiences. Walston, Blennerhassett, and Charlton (2000) set out to deliberately recruit a highlyselected pure persecutory delusion group from psychiatric services. Four individuals with persecutory delusions but withan absence of other psychopathology, intellectual impairment, overtly illogical or incoherent reasoning, or diagnoses suchas depression, mania or schizophrenia were assessed. All four cases showed intact theory of mind performance.

Because ToM difficulties have been hypothesised to explain several symptoms of psychosis, the majority of studieshave tested a group of people with schizophrenia and examined associations between symptoms of psychosis and ToMperformance. It is important to note that this provides a more stringent test than the group division studies becauseparanoid symptoms in clinical groups are rarely the only symptom present (Maric et al., 2004). Even in the studies thatgroup individuals with paranoid symptoms separately from people with negative symptoms, there may still be lowlevels of negative symptoms in the paranoid group. The possibility remains that the findings of ToM difficulties inpeople with paranoid symptoms are actually due to the presence of other symptoms.

Most studies do not find an association of positive symptoms of psychosis and ToM performance. In six studies,negative symptoms and/or thought disorder, but not delusions and hallucinations, are associated with ToM difficulties(Kelemen et al., 2005; Langdon et al., 1997; Langdon, Coltheart, Ward, & Catts, 2001; Mitchley, Barber, Gray, Brooks,& Livingstone, 1998; Mazza, De Risio, Surian, Roncone, & Casacchia, 2001; Pickup & Frith, 2001). Roncone et al.(2002) and Russell et al. (2006) found no association of positive or negative symptoms with ToM performance in theirsample, although in the Roncone et al. (2002) study a sub-sample was examined controlling for IQ and an associationwith positive symptoms was found. In two studies positive symptoms were associated with poorer ToM performance(Doody, Götz, Johnstone, Frith, & Cunningham Owens, 1998; Marjoram et al., 2005).

Six studies have examined associations with paranoid symptoms in particular. Four found no association of paranoia andToMabilities (Blackshaw, Kinderman, Hare, &Hatton, 2001; Greig, Bryson, & Bell, 2004; Langdon et al., 1997, 2001) andtwo studies did find an association (Craig et al., 2004; Harrington et al., 2006). The study of Greig et al. (2004) is the largeststudy of ToM in schizophrenia and best addresses the question of ToM and psychotic symptoms. 128 outpatients withschizophrenia were assessed on the ability to understand hints. Theory of mind performance was most strongly associatedwith thought disorder. There was an association of ToM performance with delusions but not the level of persecutorydelusions. In a regression analysis it was thought disorder, and not delusions, that predicted ToM performance.

Table 6Theory of mind and paranoid symptoms

Study Persecutory andcontrol groups

Task ToM difficulty(in paranoidgroup comparedwith non-clinicalcontrols)

Correlation ofToM performancewith paranoia orpositive symptomsof psychosiswithin wholepsychosis group

Comments

Corcoran et al.(1995)

23 paranoid symptoms(delusions of reference orpersecution or auditoryhallucinations)

Hinting task ✓

30 non-clinical controls14 psychiatric controls

Frith and Corcoran(1996)

24 paranoid (delusions orreference, misidentification,and persecution with or withoutauditory hallucinations)

First andsecond orderToM tasks

✓ The paranoid group performance was lower than thecontrol group for both first order and second orderToM tasks. However when tests were made formatched IQ sub-groups the group difference wasonly significant for the second order tasks. It is alsoof note that the paranoid patients were finding thetasks simply more difficult as assessed by amemory question.

22 non-clinical controls13 psychiatric control

Corcoran et al. (1997) 16 paranoid (delusions ofreference, misidentificationand/or persecution)

Cartoon jokesrequiringunderstanding ofmental state

✓ The paranoid group was poorer than the controlgroup for explaining jokes containing understandingof others' mental states, but did not statistically differin explaining jokes with no theory of mind component.40 non-clinical controls

Langdon et al. (1997) 20 individuals withschizophrenia

Picturesequencing task

X Poorer mentalising ability associated with negativesymptoms. There was no association withparanoid symptoms.20 non-clinical controls

Doody et al. (1998) 28 schizophrenia First andsecond orderToM tasks

✓ Performance on the second order ToM task wasassociated with the presence of positive andnegative symptoms of psychosis.

12 affective disorder19 mild learning disability18 schizophrenia andlearning disability20 non-clinical controls

Drury et al. (1998) 21 persecutory delusions A battery ofToM tasksincludingsecond orderfalse belieftasks

This study did not include a non-clinical controlgroup and therefore it cannot be determined whetherthe persecutory delusion group had ToM difficulties.However the individuals with persecutory delusionsdid not differ from the non-deluded depressedcontrols on any of the tasks. At a repeat assessmentafter symptom recovery the remitted delusion grouphad worse performance than the recovered depressedgroup on the second order false belief tasks.

12 depressedpsychiatric control

Mitchley et al.(1998) 18 individuals withschizophrenia

Irony task X Poorer performance associated with negative and notpositive symptoms of psychosis.

13 psychiatric controls

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Study Persecutory andcontrol groups

Task ToM difficulty(in paranoidgroup comparedwith non-clinicalcontrols)

Correlation ofToM performancewith paranoia orpositive symptomsof psychosiswithin wholepsychosis group

Comments

Pickup and Frith (2001) 16 paranoid First and secondorder false belieftasks.

X X There were no differences for the first order tasks. On thesecond order task a statistical trend for the paranoid groupto score lower than the controls was reported (pb .1) butthis test was one-tailed, and since results in the oppositedirection would not have been ignored, a two-tailed testwould have been better to have reported and wouldhave weakened the finding further. This trend disappearedwith matching for IQ. In regression analyses negativesymptoms and thought disorder were predictors ofToM performance.


Mazza et al. (2001) 35 individuals withschizophrenia

First and second orderfalse beliefs tasks

X ToM performance was associated with negative symptomsand not positive symptoms of psychosis.

Blackshaw et al. (2001) 25 Asperger syndrome Projectiveimagination test

X Individuals with Asperger syndrome performed morepoorly on the ToM task than the controls.

18 non-clinical controls Paranoia in the study participants was not associatedwith ToM scores.

Langdon et al. (2001) 32 individuals with psychosis ToM picturesequencing task.

X Paranoia was not associated with ToM performance.ToM performance was associated with the presence ofnegative symptoms (although this link was notsignificant when other neuropsychological task resultswere controlled for).


Roncone et al. (2002) 44 individuals withschizophrenia

First and second orderToM tasks

X ToM performance not associated with positive, negative,or disorganised symptoms, but with social functioning.In 22 individuals IQ was also assessed. When IQ wasco-varied for in this sub-sample then poorer ToMperformance was associated with the presenceof positive symptoms.

Randall et al. (2003) 15 persecutory delusions First and second orderfalse belief tasks.

✓ The delusion group performed poorer than thenon-clinical controls on both tasks.15 remitted persecutory

delusions group14 non-clinical control

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Mazza, De Risio,Surian, Roncone, andCasacchia (2001)

42 people with schizophrenia(divided into a positivesymptom group and anegative symptom group)

First and second order false belief tasks X From data presented, individuals with negativesymptoms and individuals with positive symptomsperform poorer than the controls on the ToMtasks. Individuals with negative symptomsscored significantly lower than individuals withpositive symptoms of psychosis.


Greig et al. (2004) 128 individuals with schizophreniaor schizo-affective disorder

Hinting task X A non-clinical control group was not included inthis study.Theory of mind performance was related to thoughtdisorder in particular.ToM performance was also related to levelof delusions, but not persecutory delusions.

Craig et al. (2004) 16 persecutory delusions Hinting task and the‘Reading the Mind in theEyes’ task

✓ ✓ Both the delusions group and the Asperger groupperformed more poorly than the controls on the tasks.Higher levels of paranoia were associated with poorerToM performance.

17 Asperger syndrome16 non-clinical control

Marjoram et al. (2005) 15 schizophrenia Hinting task. ✓ Participants with delusions and hallucinationsperformed significantly lower than the control group.However it is unclear whether this is due to thepresence of persecutory delusions. There was alsoa trend for negative symptoms to be associatedwith poorerToM performance.

15 affective(7 bipolar, 8 depression)15 non-clinical controls

Kelemen et al. (2005) 52 individuals with schizophrenia Eyes test X ToM performance correlated with negative but notpositive symptoms of psychosis.30 non-clinical controls

Harrington et al. (2006) 25 schizophrenia divided intopersecutory delusions group andnon-persecutory delusions group(13 and 12 respectively,McClure and Siegert, pers. com.).

1st and 2nd order verbal and non-verbal ToM tasks. ✓ ✓ Persecutory delusions associated with ToMperformance. Differences on verbal tasks.Also an association of ToM performance withformal thought disorder.

38 non-clinical controlsLangdon et al. (2006) 19 persecutory delusions False belief picture

sequencing task✓ Both clinical groups performed more poorly than the

control group.15 non-persecutory delusionschizophrenia group(nine had no delusions)21 non-clinical controls

Russell et al. (2006) 61 individuals with schizophrenia(including 15 predominatelyparanoid symptoms)

Animations task ✓ X A novel ToM task was used in this study,requiring judges to rate the participants' responses.

22 non-clinical controls ToM performance was not associated with negative orpositive symptoms of psychosis.

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Greig et al. (2004) and Harrington et al. (2006) note that mixed findings might relate to the different ToM tasks usedin studies, the different symptom groupings in studies, small sample sizes, and the idea that ToM may not be the onlyfactor contributing to persecutory experience. These issues do complicate the findings. However, the literature isbeginning to indicate that although ToM problems may be present in people with persecutory delusions they arecertainly not specific or necessary to this experience and their presence in people with paranoid experiences mayactually be due to the presence of negative symptoms and thought disorder (conceptual disorganisation andpsychomotor poverty syndromes). Difficulties with theory of mind abilities may not be central to the development ofpersecutory ideation. Walston et al.'s (2000) finding of intact ToM in individuals with pure persecutory delusions isvery much consistent with such a view. Like the attribution work, a large early episode study is required, combininggood ToM assessment and measures of different positive and negative symptoms and controlling for different positiveand negative symptoms, IQ, executive functioning and social functioning. ToM abilities have not been fully examinedin relation to dimensional measures of delusional ideation or paranoia. Such studies seem warranted and could providegood dimensional tests of symptom associations with ToM performance. Only Langdon and Coltheart (2004a, 2004b)have taken this approach. In a small student samples higher levels of schizotypy were found to be associated with lowermentalising abilities, but no consistent pattern with different schizotypy factors and ToM was found.

A very interesting study by McCabe, Heath, Burns, and Priebe (2002) merits note. They argue that if ToMdifficulties are present then they should be detectable in real-life social interactions. These researchers found thatoutpatients with positive and negative symptoms of schizophrenia actually showed intact ToM skills in conversationswith mental health professions. The patients represented mental states of others coherently and used them effectively.Furthermore, some patients knew that others did not share their delusions and viewed their beliefs as odd, and examplesare given of patients understanding implicit messages in therapists' speech. McCabe notes that some problems ofcommunication were apparent in the conversations but not those expected from ToM accounts.

The theoretical account of how ToM relates to paranoid experiences contains weaknesses. While this work hasdeveloped from the plausible argument that by definition persecutory delusions reflect incorrect judgements of theintentions of others, the ToM account of schizophrenia is much weaker in explaining exactly why a mentalisingproblem should lead to paranoid thoughts. It does not seem inevitable that difficulties in reading others' intentionswould lead to the explanation that people are disguising their intentions and forming a conspiracy. Many paranoidindividuals would say that their persecutors are not disguising their intentions and indeed make their intent all too clear.Furthermore, Walston et al. (2000) make the point that if everybody's mental states are opaque persecutory delusionsshould not be restricted to a single person or group as is often the case. In short, a mentalising difficulty may lead toincorrect inferences but why errors that are paranoid and often circumscribed?

8. The threat anticipation cognitive model of persecutory delusions

Conceptualising delusions as beliefs has provided the main theoretical opening for psychological research. AsMcReynolds (1960) notes: ‘It appears that delusional beliefs are not formally different from non-delusional beliefs.’Maher has highlighted that the beliefs result from trying to make sense of events, especially anomalous experiences thatinvite explanation. It is likely that the delusional explanations and their persistence are closely tied to reasoningprocesses. For persecutory thinking in particular, consideration of the phenomenology has identified anxiety as a keycontributory factor. These principal findings have been integrated into the threat anticipation model of paranoia(Freeman & Garety, 2004; Freeman et al., 2002, 2006). The model is explicitly built on the idea that there are multiplefactors responsible for the development and maintenance of paranoia. Furthermore, the model addresses the multi-dimensional nature of persecutory experience, highlighting specific factors for the development of delusion content,conviction, persistence, and distress (Figs. 2 and 3).

Following the influential work of Maher (1974), delusional beliefs are considered as explanations of experience.The sorts of experiences considered as the proximal source of evidence for persecutory delusions are:

• Internal feelings. Unusual or anomalous experiences are frequently key to delusional ideation. These include: being in aheightened state/aroused; having feelings of significance; perceptual anomalies (e.g. things may seem vivid or bright orpiercing, sounds may feel very intrusive); having feelings as if one is not really there (depersonalisation); and illusionsand hallucinations (e.g. hearing voices). These sorts of experiences can be caused by the processes hypothesised bytheorists such as Hemsely (1994) and Frith (1992), by the use of street drugs or by high levels of affect.

Fig. 2. Summary of the formation of a persecutory delusion.


• External events. Ambiguous social information is particularly important. This includes both non-verbal information(e.g. facial expressions, people's eyes, hand gestures, laughter/smiling) and verbal information (e.g. snatches ofconversation, shouting). Coincidences and negative or irritating events also feature in persecutory ideation.

Typically, individuals vulnerable to paranoid thinking try to make sense of internal unusual experiences by drawingin negative, discrepant, or ambiguous external information. For example, a person may go outside feeling in an unusualstate and, rather than label this experience as such (e.g. ‘I'm feeling a little odd and anxious today, probably becauseI've not been sleeping well’), the feelings are instead used as a source of evidence, together with the facial expressionsof strangers in the street, that there is a threat (e.g. ‘People don't like me and may harm me’). Persecutory delusions areviewed as explanations that contain threat beliefs about physical, social, or psychological harm.

But why a suspicious interpretation of experiences? The internal and external events are interpreted in line withprevious experiences, knowledge, emotional state, memories, personality, and decision-making processes and thereforethe origin of persecutory explanations lies in such psychological processes. Suspicious thoughts often occur in the contextof emotional distress. They are frequently preceded by stressful events (e.g. difficult interpersonal relationships, bullying,isolation). Furthermore, the stresses may happen against a background of previous experiences that have led the person tohave beliefs about the self (e.g. as vulnerable), others (e.g. as potentially dangerous), and the world (e.g. as bad) that makesuspicious thoughts more likely to occur. Living in difficult urban areas is likely to increase the accessibility of suchnegative views about others. These sorts of negative beliefs about the self and others are associated with anxiety anddepression, but anxiety may be especially important in the generation of persecutory ideation. The theme of anxiety is theanticipation of danger and it is the origin of the threat content in persecutory ideation. Anxiety may be fleeting in the

Fig. 3. Summary of the maintenance of a persecutory delusion.


generation of a paranoid thought, but paranoid thoughts will be more significant in the context of higher levels of traitanxiety. Paranoid thoughts are hypothesised to have close links with anxiety processes. Worry may keep the suspicions inmind and develop the content in a catastrophising manner. Hence in the model emotion is given a direct role in delusionformation. The anxious thoughts are hypothesised to become truly persecutory when an attribution is made concerning theintention of the perpetrators. The cause of this idea of intent is under-researched. Most often the threat beliefs contain animplicit attribution of intent. In other cases anger – often not expressed because of fear of others' reactions – maycontribute to this attribution of hostile intent, since judgements of blame and attributions of intent are central to anger.

The persecutory ideas aremost likely to become of a delusional intensitywhen there are accompanying biases in reasoningsuch as reduced data gathering (‘jumping to conclusions’) (Garety & Freeman, 1999), a failure to generate or consideralternative explanations for experiences (Freeman et al., 2004), and a strong confirmatory reasoning bias (Freeman, Garety,Kuipers, & McGuire, 2005). Social isolation may also contribute to a failure to fully review paranoid thoughts. Whenreasoning biases are present, the suspicions are more likely to become near certainties; the threat beliefs become held with aconviction unwarranted by the evidence and may then be considered delusional.

In the model there are further hypotheses concerning the maintenance of persecutory delusions and the associatedemotional reaction. For example, since the explanations are threat beliefs they will be maintained by processes thatmaintain anxiety disorders, such as self-focus and safety behaviours (see Clark, 1999). Distress is hypothesised to arisefrom two processes: aspects of the content of the delusion (e.g. beliefs about the power of the persecutor, control over the


threat, deservedness of harm) and further appraisal of the experience (e.g. worry and rumination). Beyond the definingideas of threat and attribution of intent, the content of paranoia varies in the individual case, particularly important beingaffect-laden beliefs that vary dimensionally (Freeman et al., 2001). For example, beliefs about the degree to which harm isdeserved are viewed as one aspect of the content of the delusion important in determining the level of distress, but notindicating the presence of a discrete type of paranoia. More broadly, it is of interest to note that reactions to delusions, suchas worrying, are not considered the only route to distress and the development of clinical cases— specific aspects of thecontent of beliefs make distress more likely too. Thus, emphasised in the psychological understanding of persecutoryideation are: anomalous experiences, such as hallucinations, whichmay be caused by core cognitive dysfunction and streetdrug use; affective processes, especially anxiety, worry, and interpersonal sensitivity; reasoning biases, particularly beliefconfirmation, jumping to conclusions, and belief inflexibility; and social factors, such as isolation and trauma.

9. Pitfalls in studying persecutory thinking

Developments in the understanding of paranoia have been heralded, but recognition and discussion of themethodologies and pitfalls of researching paranoia have been lacking. In this review the tendency to ignore the multi-dimensional nature of the experience and the failure to define the phenomena of interest in detail have been highlighted.Two other important issues bear upon research on delusions: the recruitment of participants and the course of illness.

Research on delusions is likely to have been affected by systematic recruitment biases. For instance, individualswith persecutory delusions that are the most strongly held, preoccupying, and distressing are probably the least likely toparticipate. Conversely, it is easier to recruit a patient into a research study as their paranoia diminishes. For purposes ofcomparison across studies, it would be helpful if researchers report the levels of belief conviction, preoccupation, anddistress of the participants. In addition, data on levels of emotional disorder are informative. Recruitment of participantsis also often ad hoc and it is often not clear whether all suitable individuals within a referral system have beenapproached. Even then it is common for half of patients who meet study criteria to refuse to participate. The demands ofeach research study will also affect patient recruitment. How representative a study group is, and the potential influenceon study results of recruitment biases, needs to be given greater attention.

Course of illness (history length and symptom outcome) are also likely to relate to recruitment biases, and may haveimportance in the interpretation of results. Individuals at first episode may be more difficult to recruit into research, incomparison with people with multiple episodes, because they are currently coming to terms with their experiences.Moreover, individuals who have symptoms that quickly and fully recover often do not attend services, particularly if they donot relapse, and therefore they seldom participate in research studies. There may be differences in participation ratesdepending upon recovery styles such as ‘sealing over’ or ‘integration’ (McGlashan, Levy, & Carpenter, 1975). There aretheoretical reasons why it is likely that the course of illness may affect the results of studies. The presentation of individualsafter their initial episodewill be affected by this first experience of symptoms and psychiatric services, particularly in relationto emotion. Depression and self blame may become more prominent and emotions such as anger, which may have beenimportant at delusion formation, may recede. This may particularly be the case in instances when there has been a longchronic course in which symptoms have never fully remitted. It is also likely that the factors that trigger relapses may bedifferent from those at first episode (e.g. the fear of relapse itself). The difficulties in recruiting participants whose symptomsquickly remit will limit what can be learnt about the factors that promote recovery. Clearly, cross-sectional studies thatinclude both individuals with symptoms that recover and individuals whose symptoms tend to persist will make it moredifficult to detect maintenance processes if the variable of recovery is not included in the analysis (a failing of previousstudies); however, longitudinal studies are generally preferable, but these are few in number (Startup et al., in press).

10. The next 10 years and beyond

In this review a number of factors have been highlighted as important to the development of persecutory delusions.However, studies havemainly concerned associations of psychological factors and persecutory thinking. It is now time forthe causal roles of these variables to be investigated, for example in experimental manipulation studies (e.g. examining theeffects of reducing or increasing anxiety). There is a need to have more longitudinal studies of natural recovery.Furthermore, psychological factors need to be studied together, including testing for interactions between variables (e.g.anxiety and the presence of anomalous experience). It is important to note that studies of delusional ideation dimensionallyin the general population enable recruitment of a larger number of participants than are possible for studies of clinical


populations and therefore provides a better means of testing complex models. In order for such work, however, to beconsidered convincing for the psychosis field, it needs to be carried out in the context of detailed scrutiny of both thesimilarities and differences between clinical cases of persecutory delusions, non-clinical cases of persecutory delusions,and non-clinical paranoid ideation.

Aside from psychological factors, which have been the focus of the review, there is considerable work needed on thephenomenological examination of persecutory ideation. As distress is often what marks out clinical from non-clinicalcases, an understanding of its causes should be a higher priority, and content of the beliefs is one cause of distress. Onefuture line of clinically relevant research would be the investigation of change in delusion content. How do theimportant emotional content and associated appraisals in delusional systems change with recovery? How do theinternal contents of a delusion change in relation to each other? This type of approach has the potential to form a linkwith patient views of recovery. Furthermore, persecutory thinking can be associated with other delusion sub-types,particularly reference but also sometimes grandiose, and the inter-relationships between symptoms need to beconsidered. For example, persecutory thinking often builds upon ideas of reference. But it is also the case that it will beimportant to identify the factors that distinguish, for example, paranoid from grandiose thinking or anxious thinking.

From the review, ten research questions for future investigation are apparent:

1. Can psychological models of paranoia be shown to have high accuracy in explaining the occurrence ofpersecutory thoughts?

2. How do psychological factors relate to the different dimensions of delusional experience?3. What are the psychological factors that distinguish clinical from non-clinical paranoia?4. Can it be shown that psychological factors are causal in paranoid thinking?5. Do psychological factors interact in the development of paranoia?6. What factors distinguish the development of persecutory ideation from the development of grandiosity?7. What distinguishes the development of paranoid from anxious fears?8. What are the key emotion-associated aspects of paranoid thoughts and how do they change with time?9. How do psychological processes relate to social and biological factors potentially associated with paranoia?

10. Can the developments in the understanding of paranoia be used to improve treatments?

In the past, paranoia was too often studied only in the context of severe mental illness and, even then, researcherswere trying to explain a diagnosis such as schizophrenia rather than persecutory thinking itself. Researchers over thelast 10 years have begun to free paranoia from this association, and view it as a phenomenon to be explained in its ownright, linking it with suspicious thoughts apparent in many people in the general population. Moreover, analogies withthe study of depressive and anxious thinking are being made. The key questions for the future study of persecutorythinking are now becoming apparent and over the next 10 years there are likely to be great strides in understanding inthis important clinical area as it receives greater attention. These developments in understanding will then need to betranslated into improvements in the emerging cognitive–behavioural treatments for paranoid thoughts (Freeman et al.,2006).

Acknowledgement

Daniel Freeman is supported by a Wellcome Trust Fellowship.

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