Biological Aspects of AdolescenceSam Mathews, Ph.D.

School of Psychological and Behavioral SciencesThe University of West Florida

• Puberty

• Changes in physical attributes

• Neurological changes

• Health practices

Biological Bases

• The Endocrine System and the Puberty Process:– HypothalamusGonadotropin Releasing

Hormones (GRH)Pituitary Gland– Pituitary gland GonadotropinGonads

(ovaries/testes)– Gonadsstimulate release of sex hormones

(estrogens/androgens) that stimulate secondary sex characteristics

Puberty Process:

• Process begins approximately 2 years prior to initial secondary sex characteristic changes;

• Hypothalamous secretions typically increase during deep sleep;

• Males and females produce both estrogens and androgens but in different proportions;

Puberty Process: Physical Changes

• Secondary sex characteristics– Body/pubic hair (males and females)– Breast enlargement (most obvious in females)– Increase in growth rate (females and males)– Changes in voice (most obvious in males)– For females, increase in fat to muscle cell

ratio (increase in fat cells relative to muscle cells)

Puberty Process: Physical Changes

• For females: as level of estrogen increases, the hypothalamus produces Gonadotropin Inhibiting Hormones (GIH). This inhibits the production of estrogen by the ovaries;

• The periodic cycle of increases and decreases in estrogen controls the ovulation cycle.

• Estrogen is stored in fat cells so the increase in fat cells relative to muscle cells allows the critical level of estrogen necessary for ovulation.

Neurological Changes

• Myelinization– Fatty tissue surrounding nerve cells in the

brain– Increases the efficiency of transmission of

signals across the synaptic junctions in the brain

– Made up of cholesterol and proteins– Rapid increase of myelinization during and

after puberty through adolescence

Neurological Changes

• Elaboration of synaptic connections– Neurons form new connections based on

experience throughout the lifespan;– Plasticity still a major force—brain responds

to stimulation

Neurological Changes

• Frontal and pre-frontal cortex major area of development across adolescence– Maturation of neurological systems that allow:

• Planning• Regulation of emotion• Monitoring

– Prediction based on this is that across adolescence, ability to forecast, anticipate long-term outcomes and recognize risk is limited

Health Practices and Puberty Process

• Nutrition—balanced diet including appropriate levels of carbohydrates (myelinization)

• Sleep—reasonable opportunities for deep sleep (supports initiation and maintenance of puberty process)

• Limited alcohol consumption—some evidence that alcohol interferes with hormonal balance of pubescent females

Puberty Process: Pre and Early Adolescents

• Direct effects hypothesis—the onset of puberty, in itself, brings about an unstable and stormy time in one's life

• Mediated effects hypothesis—the impact of the onset of puberty is the result of the interaction of cultural and psychological factors with the biological changes

Social Changes Associated with Puberty

As physical changes occur, others treat the young adolescent differently (self-fulfilling prophecy);

– societal expectations change--schooling; position in the family--perhaps caring for younger siblings, increased household responsibility

– target for marketing--music, clothes, alcohol, tobacco

Pubertal Timing and Social-Cultural-Emotional Factors

• “Early maturing girls who experienced higher levels of stressful live events tend to report more depressive symptoms in the junior high (gr.7, 8. 9) and early high school years (gr 10-11)”

• (Ge, Conger, & Elder, 2001)

Pubertal Timing and Social-Cultural-Emotional Factors

• Early maturation, early onset of dating, and emotional distress predicts initiation of substance use (tobacco, alcohol, marijuana) across two year period…most likely due to interactions with older peers…

Pubertal Timing and Social-Cultural-Emotional Factors

A review of studies examining pubertal status, parental and peer factors, the following was observed:

“…peers and parents appear to account for much of the total variance (77%) in early substance use. “

Brent Walden, Matt McGue, William G. Iacono, S. Alexandra Burt, Irene Elkins (2004)

Pubertal Timing and Social-Cultural-Emotional Factors

• “Many of the studies we have reviewed confirm current thinking that adolescence does not inevitably spell trouble” (Buchanan, Eccles, & Becker, 1992)

Gene—Environment Effects• Passive Genotype Environment Effect

– Biological parent(s) provide environmental structure; most frequently seen in infants and younger children

• Evocative Genotype Environment Effect– Genotypic behaviors evoke positive responses from

the environment; frequently seen in extended families and peers; must have access to others

• Active Genotype Environment Effect– Individuals actively seek out or create environments

that match their genotypic attributes; frequently seen in older children and adolescents; must have access to environments

– (Sandra Scarr, 1993)

Pubertal Timing and Social-Cultural-Emotional Factors

• Resiliency: ability to encounter stressful and risky situations and emerge without injury or harm

• Resiliency factors for adolescents (and others) can include:– Family– Peers– Teachers– Other significant individuals

Discussion Questions:

• Describe your own experience as you matured into puberty?

• How did your parents prepare you for puberty and entrance into adolescence?

• As you think about the information from the text on rites of passage into puberty, what rites of passage did you experience as you moved from childhood to adolescence?

• How did your experiences differ from those described in the text?