Cannabis Its Effects On Children And Young People
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Drug use amongst young people Cannabis is the most widely used illegal drug in Britain and the third most commonly consumed drug after alcohol and tobacco. 1 Use is most prevalent amongst young people, with 29 per cent of 15-year-olds in 2000 reporting that they had used it in the past year. 2 Figures based on the British Crime Survey show that in 2000, an estimated two million 16- to 29-year-olds reported using cannabis at least once in the previous year, and around a million and a half had used it at least once in the previous month. 1 Young people in Britain are more likely to have tried illegal drugs, including cannabis, than their counterparts in Europe. 3 Recent evidence from the Health Related Behaviour Questionnaire surveys, which are carried out annually in a selection of UK schools, points to a fall in the proportion of young people who report trying illegal drugs, including cannabis, since the mid-1990s. 4 However, studies conducted throughout the 1990s in the UK consistently show that the age at which illegal drugs are first tried is falling and that cannabis dominates drug trying and use throughout the teenage years. 5 This earlier onset of first drug use may predict a longer drug-using career, and the likelihood of related problems. 6 Risks to physical and mental health Whilst the toxicity of cannabis is extremely low, 7 and there is no evidence that anyone has ever died as a direct and immediate consequence of using cannabis, both short- and long-term use of the drug have numerous implications for physical and mental health. Mental health A single dose of cannabis for an inexperienced user, or a larger than usual dose for an experienced user, can sometimes induce a variety of unpleasant psychic effects, including anxiety, panic and paranoia. 8 Some researchers have suggested that cannabis can produce longer lasting mood disorders or psychotic disorders and there are clinical reports of cannabis-induced psychosis-like states lasting for a week or more. 9 However, there is little evidence that cannabis alone produces a psychosis that persists after the period of intoxication. 7 The scientific literature indicates general agreement that heavy cannabis use can precipitate schizophrenic episodes but cannot cause the underlying psychotic disorder. 10,11,12 A longitudinal study of 50,000 Swedish male conscripts found that the risk of receiving a diagnosis of schizophrenia over the next 15 years increased linearly with the number of times that an individual had used cannabis by the age of 18. 13 However the methodology of this study has been criticised. 14 Others have argued that it is unlikely that cannabis use can precipitate schizophrenic illness that would not otherwise have occurred, since the incidence of schizophrenia has not increased in countries such as Australia, which have seen dramatic increases in adolescent cannabis use in the past twenty years. 7 The precise relationship of cannabis use to psychoses such as schizophrenia has yet to be clarified. 15 Physical health Cannabis increases the heart rate and lowers the blood pressure but cardiovascular changes associated with cannabis are not reported as posing a health problem for healthy, young cannabis users. 16 Long-term heavy cannabis smoking carries the same kinds of risks of respiratory disorders as smoking tobacco. Cannabis smoke contains many of the components of tobacco smoke. In the UK the most common method of use is in the form of cannabis resin mixed with tobacco. Although the frequency of use, even in regular smokers, may be less than for tobacco, cannabis smokers tend to inhale more deeply and hold the smoke in the lungs for longer, thus increasing the respiratory ‘burden’ of the inhaled material. 7 Chronic heavy cannabis smoking may lead to acute and chronic bronchitis although it has not been established that it causes Chronic Obstructive Pulmonary Disease. 16 One of the few epidemiological studies to evaluate the association between cannabis and cancer was conducted in the US on a cohort of about 65,000 men and women aged 15–49 years old. Apart from an increased risk of prostate cancer in men who did not smoke tobacco, no association was found between cannabis use and other cancers. 18 However the cohort was relatively young and the development of lung cancer requires a long exposure to smoking, with most cannabis users quitting before this level of exposure is achieved. 16 Cellular and molecular studies have provided strong evidence that cannabis smoke is carcinogenic, 19 and the tar from cannabis smoke also induces mutations similar to those produced by tar from the same quantity of tobacco. 20 Moreover, the effects of cannabis and tobacco are additive. 21 Thus, in relatively young smokers of cannabis, particularly those who smoke both cannabis and tobacco, cannabis is implicated as a risk factor for lung cancer. 16 Dependence A regular user of cannabis will not suffer from severe physical withdrawal symptoms, a fact which has prompted many to argue that the drug is not capable of inducing dependence. However, in the US, cannabis dependence is among the most common form of illicit drug dependence in the population 22 and a recent Australian study found that almost one third of cannabis users met criteria for cannabis dependence. 23 As many as one in 10 cannabis users who want to stop or cut down, find it very difficult to do so, and continue to use the drug, despite the adverse effects it has on their life. 7,22 Effects of cannabis use on educational attainment Cannabis use typically starts during adolescence 24 which has led to concerns about its potentially adverse effects on educational performance. Cross-sectional studies have shown significant associations between cannabis use and a range of measures of educational performance including lower grade point average, 25 less satisfaction with school, 26 negative attitudes to school, 27 and poor school performance. 28 However, these results cannot be used to determine whether cannabis use causes poor educational performance, poor educational performance leads to cannabis use or whether both outcomes are a reflection of common risk factors. 29 Nonetheless, a number of longitudinal studies have indicated that early cannabis use may significantly increase risks of subsequent poor school performance and, in particular, early school leaving. 30,31 Explanations for the association between early cannabis use and educational attainment include the possibility that cannabis use causes ‘amotivational syndrome’, a description for a state in which users become apathetic, withdrawn, unmotivated and show evidence of impaired memory, concentration and judgement, 32 or that it causes cognitive impairment. 33 However a recent review of the literature concluded that there was little support for these hypotheses and suggested that the apparent effects of early cannabis use on educational attainment are related more to the social context within which cannabis is used and accessed rather than to any biological effects of cannabis. 29 In one of the few studies to focus specifically on the effects of early cannabis use, Fergusson and Horwood found that early cannabis use increases the chance of the user adopting an unconventional lifestyle characterised by relationships with delinquent and substance-using peers and disengagement from conventional social roles, including completing education and gaining employment. 34 Cannabis: its effects on children and young people Produced by the Library & Information Service of the National Children’s Bureau together with Barnardo’s as a joint commitment to share current research, development, policy and practice. no. 189 high light NATIONAL CHILDREN’S BUREAU
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Transcript of Cannabis Its Effects On Children And Young People
Drug use amongst young peopleCannabis is the most widely used illegal drug in Britain and the thirdmost commonly consumed drug after alcohol and tobacco.1 Use is mostprevalent amongst young people, with 29 per cent of 15-year-olds in2000 reporting that they had used it in the past year.2 Figures based onthe British Crime Survey show that in 2000, an estimated two million16- to 29-year-olds reported using cannabis at least once in the previousyear, and around a million and a half had used it at least once in theprevious month.1 Young people in Britain are more likely to have triedillegal drugs, including cannabis, than their counterparts in Europe.3
Recent evidence from the Health Related Behaviour Questionnairesurveys, which are carried out annually in a selection of UK schools,points to a fall in the proportion of young people who report tryingillegal drugs, including cannabis, since the mid-1990s.4 However,studies conducted throughout the 1990s in the UK consistently showthat the age at which illegal drugs are first tried is falling and thatcannabis dominates drug trying and use throughout the teenage years.5
This earlier onset of first drug use may predict a longer drug-usingcareer, and the likelihood of related problems.6
Risks to physical and mental health Whilst the toxicity of cannabis is extremely low,7 and there is noevidence that anyone has ever died as a direct and immediateconsequence of using cannabis, both short- and long-term use of thedrug have numerous implications for physical and mental health.
Mental health
A single dose of cannabis for an inexperienced user, or a larger thanusual dose for an experienced user, can sometimes induce a variety ofunpleasant psychic effects, including anxiety, panic and paranoia.8
Some researchers have suggested that cannabis can produce longerlasting mood disorders or psychotic disorders and there are clinicalreports of cannabis-induced psychosis-like states lasting for a week ormore.9 However, there is little evidence that cannabis alone produces apsychosis that persists after the period of intoxication.7
The scientific literature indicates general agreement that heavycannabis use can precipitate schizophrenic episodes but cannot causethe underlying psychotic disorder.10,11,12 A longitudinal study of 50,000Swedish male conscripts found that the risk of receiving a diagnosis ofschizophrenia over the next 15 years increased linearly with the numberof times that an individual had used cannabis by the age of 18.13
However the methodology of this study has been criticised.14 Othershave argued that it is unlikely that cannabis use can precipitateschizophrenic illness that would not otherwise have occurred, since theincidence of schizophrenia has not increased in countries such asAustralia, which have seen dramatic increases in adolescent cannabisuse in the past twenty years.7 The precise relationship of cannabis useto psychoses such as schizophrenia has yet to be clarified.15
Physical health
Cannabis increases the heart rate and lowers the blood pressure butcardiovascular changes associated with cannabis are not reported asposing a health problem for healthy, young cannabis users.16
Long-term heavy cannabis smoking carries the same kinds of risks ofrespiratory disorders as smoking tobacco. Cannabis smoke containsmany of the components of tobacco smoke. In the UK the most commonmethod of use is in the form of cannabis resin mixed with tobacco.Although the frequency of use, even in regular smokers, may be lessthan for tobacco, cannabis smokers tend to inhale more deeply and holdthe smoke in the lungs for longer, thus increasing the respiratory‘burden’ of the inhaled material.7 Chronic heavy cannabis smoking maylead to acute and chronic bronchitis although it has not been establishedthat it causes Chronic Obstructive Pulmonary Disease.16
One of the few epidemiological studies to evaluate the associationbetween cannabis and cancer was conducted in the US on a cohort ofabout 65,000 men and women aged 15–49 years old. Apart from anincreased risk of prostate cancer in men who did not smoke tobacco, noassociation was found between cannabis use and other cancers.18
However the cohort was relatively young and the development of lungcancer requires a long exposure to smoking, with most cannabis usersquitting before this level of exposure is achieved.16
Cellular and molecular studies have provided strong evidence thatcannabis smoke is carcinogenic,19 and the tar from cannabis smoke alsoinduces mutations similar to those produced by tar from the samequantity of tobacco.20 Moreover, the effects of cannabis and tobacco areadditive.21 Thus, in relatively young smokers of cannabis, particularlythose who smoke both cannabis and tobacco, cannabis is implicated asa risk factor for lung cancer.16
DependenceA regular user of cannabis will not suffer from severe physicalwithdrawal symptoms, a fact which has prompted many to argue thatthe drug is not capable of inducing dependence. However, in the US,cannabis dependence is among the most common form of illicit drugdependence in the population22 and a recent Australian study found thatalmost one third of cannabis users met criteria for cannabisdependence.23 As many as one in 10 cannabis users who want to stop orcut down, find it very difficult to do so, and continue to use the drug,despite the adverse effects it has on their life.7,22
Effects of cannabis use on educational attainment Cannabis use typically starts during adolescence24 which has led toconcerns about its potentially adverse effects on educationalperformance. Cross-sectional studies have shown significantassociations between cannabis use and a range of measures ofeducational performance including lower grade point average,25 lesssatisfaction with school,26 negative attitudes to school,27 and poorschool performance.28 However, these results cannot be used todetermine whether cannabis use causes poor educational performance,poor educational performance leads to cannabis use or whether bothoutcomes are a reflection of common risk factors.29 Nonetheless, anumber of longitudinal studies have indicated that early cannabis usemay significantly increase risks of subsequent poor schoolperformance and, in particular, early school leaving.30,31
Explanations for the association between early cannabis use andeducational attainment include the possibility that cannabis use causes‘amotivational syndrome’, a description for a state in which usersbecome apathetic, withdrawn, unmotivated and show evidence ofimpaired memory, concentration and judgement,32 or that it causescognitive impairment.33 However a recent review of the literatureconcluded that there was little support for these hypotheses andsuggested that the apparent effects of early cannabis use on educationalattainment are related more to the social context within which cannabisis used and accessed rather than to any biological effects of cannabis.29
In one of the few studies to focus specifically on the effects of earlycannabis use, Fergusson and Horwood found that early cannabis useincreases the chance of the user adopting an unconventional lifestylecharacterised by relationships with delinquent and substance-usingpeers and disengagement from conventional social roles, includingcompleting education and gaining employment.34
Cannabis: its effects on children and young people
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Cannabis as a gateway drugThe relationship between cannabis use and the use of other drugs,including alcohol and nicotine, during adolescence and into adulthoodis extremely complex. The fact that cannabis is typically the first illicitdrug that is used by those who subsequently develop problems withheroin and cocaine use,35 has led to claims that use of cannabis leadsdirectly to use of more harmful drugs. However it is difficult toestablish whether cannabis plays a causal role in this sequence, asadolescents who start using cannabis early and become heavy users arefound to be independently at higher risk of using other drugs.34 The‘stepping-stone’ theory posits that cannabis use leads inexorably toharder drug use, either because it causes a chemical reaction in the brainthat makes the user desire new drugs, or because cannabis users becomeaccustomed to the mild high of cannabis and begin to crave the moreintense high offered by other drugs. This theory has been discounted inboth British and US reviews16,36 and does not account for the hugemajority of cannabis users who do not progress to drugs like heroin.
The other main theory describing the relationship between cannabis useand use of other drugs is known as ‘the Gateway Hypothesis’. Thisclaims that drug users will generally progress from legitimate drugssuch as alcohol and nicotine to various forms of illicit drug use.37
Gateway theory is a metaphor for the individual having access to newgates after entering the first gate but not necessarily choosing to openthese new gates. Therefore, those using illicit drugs will invariably haveused alcohol or tobacco but not all those using illicit drugs such ascannabis will move on to using more harmful illicit drugs such asheroin and cocaine.36 This is a stage theory of substance misuse, and hasbeen strongly supported by a recent comprehensive New Zealandstudy.34 The main explanations for the way cannabis acts as a gatewayare: some cannabis users share common personality profiles orenvironmental conditions with the users of more harmful drugs;7 usersdo not find cannabis brings the harm that has been attributed to it, sotheir expectations of risk from other drugs are lowered;38 and cannabisuse brings users into contact with people using or selling other illicitdrugs, which they may then try.7,34
ConclusionCompared with other drugs, including alcohol and tobacco, cannabishas relatively few adverse effects that are immediately obvious and doesnot appear to cause severe addiction problems. However, there are anumber of physical and psychological problems associated with its use,both in the short and long term. Evidence exists that young people aretrying drugs at an earlier age, and this has implications for futureresearch into the long-term health and social effects of cannabis. Thereis also evidence that a link exists between cannabis and more harmfuldrugs such as heroin and cocaine, although this link is not causal and islikely to be due, in part, to the fact that the current illegality of cannabisputs individuals in situations where they are more likely to experiencepeople using and supplying more harmful drugs. The proposedreclassification of cannabis may remove one significant adverse effectof use, which is the criminalising of young people for possession of thedrug, but the link to harder drugs will not be entirely removed whilstcannabis supply remains in the hands of illegal suppliers.
Claire O’Kane January 2002
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