The Teenage Brain

““Youth are heated by nature Youth are heated by nature as drunken men by wine.” as drunken men by wine.”

AristotleAristotle

New Thinking Scientists once thought that all of the Scientists once thought that all of the

brain’s cells were present at birth and that brain’s cells were present at birth and that all connections were established and “hard all connections were established and “hard wired” in infancy and early childhood wired” in infancy and early childhood The brain has reached 90 percent of its The brain has reached 90 percent of its

full size by the age of 6full size by the age of 6 New research shows the brain continues to New research shows the brain continues to

evolve through the teens & early twentiesevolve through the teens & early twenties This may help explain why teens act the This may help explain why teens act the

way they do.way they do.

The Chicken & The Egg: The Effect of Puberty

Adolescent brain development is Adolescent brain development is influenced by pubertal maturationinfluenced by pubertal maturation

Puberty is the onset of sexual Puberty is the onset of sexual maturationmaturation

Includes changes in three separate Includes changes in three separate neuroendocrine axes: neuroendocrine axes: GonadalGonadal Adrenal androgensAdrenal androgens GrowthGrowth

Neuroendocrine Changes Gonadarche: turning on the hypothalamic-Gonadarche: turning on the hypothalamic-

pituitary-gonadal axis pituitary-gonadal axis Leads to estrogen production & breast Leads to estrogen production & breast

development in girls development in girls Testosterone production & maturation of male Testosterone production & maturation of male

genitalia in boys. genitalia in boys. Adrenarche: turning on adrenal androgen Adrenarche: turning on adrenal androgen

production in both boys & girls production in both boys & girls Contributes to development of secondary sex Contributes to development of secondary sex

characteristicscharacteristics Growth: growth hormone secretion Growth: growth hormone secretion

Rapid physical growth Rapid physical growth Changes in body compositionChanges in body composition. .

The Role of Puberty in Brain Development

Brain changes that contribute to the Brain changes that contribute to the cascade of hormone changescascade of hormone changes

Pubertal brain changes that are caused Pubertal brain changes that are caused by maturational hormonal increasesby maturational hormonal increases

Maturational brain changes that occur Maturational brain changes that occur relatively independent of pubertyrelatively independent of puberty

Maturational processes linked to Maturational processes linked to puberty in indirect ways puberty in indirect ways e.g., new experiences that occur as a e.g., new experiences that occur as a

result of sexual maturationresult of sexual maturation

Teen Brains Are Different Most of the new developments in the Most of the new developments in the

study of teenage brains comes from study of teenage brains comes from magnetic resonance imaging (MRI)magnetic resonance imaging (MRI) Studies by Dr. Jay GieddStudies by Dr. Jay Giedd - Child Psychiatry - Child Psychiatry

Branch of NIMHBranch of NIMH Images show thickening in gray matter Images show thickening in gray matter

on the outer part of the brain peaks at on the outer part of the brain peaks at age 11 in girls and at age 12 in boys.age 11 in girls and at age 12 in boys.

During the teen years, the brain trims During the teen years, the brain trims back excess cells and connectionsback excess cells and connections

Adolescent Risk Taking

Mortality rises during adolescence, Mortality rises during adolescence, then comes back down then comes back down 32% of deaths during this period 32% of deaths during this period

result from motor vehicle accidents result from motor vehicle accidents mortality is 2 to 3 times greater in mortality is 2 to 3 times greater in

males than females.males than females. Some aspects of teenage behavior Some aspects of teenage behavior

(e.g. mood swings & risk taking) may (e.g. mood swings & risk taking) may be explained by brain developmentbe explained by brain development

Risk Taking: It’s All in Your Head

MRI shows one of the last parts of the brain to MRI shows one of the last parts of the brain to complete maturation is the prefrontal cortexcomplete maturation is the prefrontal cortex This is the part of the brain responsible for This is the part of the brain responsible for

planning, judgment and self-controlplanning, judgment and self-control Maturation of neural networks governing self-Maturation of neural networks governing self-

regulation doesn't occur until late in regulation doesn't occur until late in adolescenceadolescence

Sensitivity to rewards is different in Sensitivity to rewards is different in adolescents than in adults adolescents than in adults Seek higher levels of stimulation to achieve the Seek higher levels of stimulation to achieve the

same feeling of pleasuresame feeling of pleasure Increased risk-taking during adolescence is Increased risk-taking during adolescence is

normal and biologically drivennormal and biologically driven

Other Important Developments

White matter increases linearly White matter increases linearly during adolescenceduring adolescence

The cerebellum also grows in The cerebellum also grows in volume. volume.

Adolescence is the most efficient Adolescence is the most efficient time for motor learningtime for motor learning

Adolescence & Schizophrenic Brains

Studies of adolescent brain development Studies of adolescent brain development may lead to greater understanding of may lead to greater understanding of schizophrenia & vice versaschizophrenia & vice versa David A. Lewis - University of PittsburghDavid A. Lewis - University of Pittsburgh

Schizophrenics show impaired maturation Schizophrenics show impaired maturation of the circuitry of the prefrontal cortex. of the circuitry of the prefrontal cortex. working memory is impairedworking memory is impaired

Connections regulating the transmission Connections regulating the transmission of dopamine must be intact for working of dopamine must be intact for working memory to function properly. memory to function properly.

The Connection

A reduction in excitatory synapses A reduction in excitatory synapses occurs during adolescenceoccurs during adolescence

This reduction is even greater in This reduction is even greater in schizophrenia. schizophrenia.

The reduced number of excitatory The reduced number of excitatory synapses may explain the impairment synapses may explain the impairment of working memory in schizophrenia of working memory in schizophrenia and the onset of its symptoms during and the onset of its symptoms during adolescence. adolescence.

MRI of Schizophrenic Brain

Brain scan of Schizophrenic patient (right) and Brain scan of Schizophrenic patient (right) and normal brain (left). The normal brain shows normal brain (left). The normal brain shows more activity in the frontal cortex. more activity in the frontal cortex.

Stress and Brain Development

Changes in reproductive and stress Changes in reproductive and stress hormones can influence behavior.hormones can influence behavior.

Hormonal changes during Hormonal changes during adolescence can also trigger adolescence can also trigger depression. depression.

Stress can cause hormone changes Stress can cause hormone changes by increasing cortisol levels. by increasing cortisol levels.

Brain Plasticity, Stress & Hormones

Experiences and behaviors encountered early Experiences and behaviors encountered early in life can effect how the brain changes to in life can effect how the brain changes to adapt to its environment. adapt to its environment.

Repeated stress increases anxiety and Repeated stress increases anxiety and aggression.aggression.

Stress can cause physical changes in the brain Stress can cause physical changes in the brain that result in changes in behavior as well. that result in changes in behavior as well.

Stress increases the size of the amygdala and Stress increases the size of the amygdala and causes shrinkage of the hippocampus. causes shrinkage of the hippocampus.

Brain changes can also be observed in studies Brain changes can also be observed in studies of patients with major depression. of patients with major depression.