Daniel Krowchuk, M.D.Departments of Pediatrics and Dermatology

Wake Forest University School of Medicine

ObjectivesDescribe changes in brain structure and

function that occur during adolescenceDiscuss the implications of these changes

with respect to adolescent behavior and health promotion strategies

The leading cause of death for teenagers in the U.S. isA. AIDSB. cancerC. homicideD. suicideE. unintentional injury

Deaths, Percent of Total Mortality, and Death Rates by Cause, 15-19 year olds, U.S., 2004

Cause Number

Percent

Rate/100,000

All Causes 13,706 100.0 66.1

Unintentional injury

6,825 49.8 32.9

Homicide 1.932 14.1 9.3

Suicide 1,700 12.4 8.2

Malignancy 731 5.3 3.5

Heron M. National Vital Statistics Reports 2007;56(5)

What percent of high school seniors report having been drunk?A. 25%B. 40%C. 55%D. 70%E. 85%

Lifetime Prevalence of Use (%) of Various Substances by High School Seniors

Substance

1980

1985

1990

1995

2000

2003

2006

2007

2008

Any illicit drug

65.4 60.6

47.9

48.4

54.0 51.1

48.2 46.8 47.4

Marijuana

60.3 54.2

40.7

41.7

48.8 46.1

42.3 41.8 42.6

LSD 9.3 7.5 8.7 11.7

11.1 5.9 3.3 3.4 4.0

Ecstasy - - - - 11.0 8.3 6.5 6.5 6.2

Cocaine 15.7 17.3

9.4 6.0 8.6 7.7 8.5 7.8 7.2

Been drunk

- - - 63.2

62.3 58.1

56.4 55.1 54.7

Cigarettes

71.0 68.8

64.4

64.2

62.5 53.7

47.1 47.1 44.7

http://monitoringthefuture.org/ (1/09)

Physical Development (Puberty)

Social and Emotional Maturation

Cognitive Development

Early Adolescence

Middle Adolescence

Late Adolescence

10 – 13 years 14 – 16 years 17 – 21 years

Social and Emotional MaturationEmotional separation from parentsDevelop a sense of personal identity and self-

imageIdentify with a peer groupExplore romantic relationships

Hazen E, et al. Pediatr Rev 2008;29:161-168

Cognitive DevelopmentIncreased ability to think abstractlyGreater impulse controlImproved ability to assess risk vs. rewardImproved use of working memory (the

information in memory available for working on a problem)

Hazen E, et al. Pediatr Rev 2008;29:161-168Casey BJ. Ann NY Acad Sci 2008;1124:111-126

Cognitive alterations are associated with

changes in brain structure and function

Neuroanatomy ReviewGray matter (cerebral cortex):

Contains nerve cell bodiesProcesses and routes informationIncreases in pre-adolescence then

decreases

White matter:Composed of nerve cell extensions (axons) that convey

information (e.g., from gray matter)Color results from myelin coating of axons (acts as

insulation that allows nerve impulses to travel more rapidly and efficiently)

Changes in Brain AnatomyEach new experience results in new

connections between neurons By the end of adolescence, the brain

contains10 - 100 billion neurons

Forming 100 trillion connections with one other100 billion – 1 trillion support cells

Increased intelligence, reasoning, problem-solving

Weinberger DR, et al. The Adolescent Brain: A Work in Progress. National Campaign to Prevent Teen Pregnancy; 2005.

Changes in Brain AnatomyPruning

Information that is regularly used is retained – that which is unimportant or used infrequently is lost as the result of pruning (a loss of cells or connections) Adolescents may lose 15% of synaptic connections/year

(compared with 1-2% for adults) Results in greater efficiency

Myelination Fatty covering of axons that acts as insulation

Permits more rapid (100-fold) and efficient communication

Increases into the third decade

Weinberger DR, et al. The Adolescent Brain: A Work in Progress.National Campaign to Prevent Teen Pregnancy; 2005.

Lateral prefrontal cortex(Cognitive control)-Impulse control-Setting priorities-Formulating plans-Decision-making-Envisioning consequences of actions

Limbic system(Socioemotional)-Impulsiveness-Sensation-seeking

Risky Business – The Role of Peers Among adolescents, many high risk behaviors

take place in groupsSubstance useReckless drivingCrimes

Are adolescents more susceptible to the influences of risk-prone peers?

Risky Business – The Role of PeersRisky decision-making

asessed in:106 adolescents (13-16

yrs)105 youths (18-22 yrs)95 adults (>24 yrs)

Decision-making assessed using video gameAlone In group with 2 other

subjects who could offer advice

- Watch car move across screen until yellow traffic light appears- Stop car before red light and wall appear- More points the further the car moved without crashing into wall

Gardner M, Steinberg L. Dev Psychol 2005;41:625-635

Risk Preference Scale5 hypothetical scenarios

Having sex without a condomRiding in a car driven by someone who has

been drinkingTrying a new drug one knows nothing aboutBreaking into store to steal something one

wantsDriving over 90 mph on highway at night

Ranked 1 (risks are much greater than benefits) to 4 (benefits are much greater than risks)

Gardner M, Steinberg L. Dev Psychol 2005;41:625-635

Risky Business – The Role of PeersYounger individuals:

Allowed car to move further after yellow lightChose riskier course of action on

questionnaireWere more likely to be affected by peer

influences

Gardner M, Steinberg L. Dev Psychol 2005;41:625-635

Risk-Reward and Brain ActivityNucleus accumbens

Component of the limbic systemInvolved in processing rewards

Cortex receives stimulus indicating reward Nucleus accumbens and other areas are

activated leading to repetition of the gratifying behavior

Develops earlier than the prefrontal cortex

Galvan A, et al. J Neurosci 2006;26:6885-6892

Risk-Reward and Brain ActivityFunctional MRI performed during tasks

weighing risk and rewardAdolescents activate the nucleus

accumbens more than adultsNucleus accumbens activity correlates with

anticipation of a positive consequence of a risky behavior (which, in turn, correlates with the likelihood of engaging in risky behaviors) – more pronounced in adolescents

Ad

Galvan A, et al. J Neurosci 2006;26:6885-6892Galvan A, et al. Dev Sci 2007;10:F8-F14

Substance Use and the BrainLimbic system - prefrontal cortex

connections grow into early adulthood.Certain of these neurons use dopamine to

relay messagesThese neurons increase capacity for more

mature thought (choices based on memory not impulse)

Cocaine and amphetamines target these dopaminergic neurons.

Weinberger DR, et al. The Adolescent Brain: A Work in Progress. National Campaign to Prevent Teen Pregnancy; 2005.

“Hot” and “Cold” Cognition“Hot” cognition

Decision made in an emotionally-charged situationAdolescent surrounded by peers in a stimulating

environment may make an emotionally-based decision

“Cold” cognitionDecision made in a calmer, quieter environmentAdolescent may make a more intellectual,

consequence-based decisionSocial skills training (i.e., role-playing) may be

beneficial in moderating “hot” cognitions.

Recognizing EmotionsAdolescents often misinterpret body

language and words that are spokenA parent stares at their adolescent waiting for

a response to a question – the adolescent interprets the stare as the parent being angry.

An adolescent looks across the lunchroom at an acquaintance; the acquaintance happens to turn her head in the other direction – the adolescent may interpret that she has been shunned.

Adapted from Feinstein S. Secrets of the Teenage Brain. Thousand Oaks, Ca: Corwin Press; 2004

Recognizing EmotionsComplex network of brain regions involved

in recognizing Basic emotions (fear)Social emotions (guilt, embarrassment,

shame)Network includes:

AmygdalaMedial prefrontal cortexAnterior insulaSuperior temporal sulcus

Blakemore S-J. Nat Rev Neurosci 2008;9:267-276

Do Adolescent and Adults Differ?Adults and adolescents presented with

the photograph of a woman with an expression of fear on her faceAll adults correctly interpreted the

emotion as fearHalf of adolescents thought that the

woman expressed shock or surprise

Blakemore S-J. Nat Rev Neurosci 2008;9:267-276

Processing Emotions19 adolescents (10 - 18 years) and 10 adults

(22 – 32 years) underwent functional MRI scanning1 while thinking about scenarios involving:Basic emotions (e.g., disgust, fear)Social emotions (e.g., embarrassment, guilt,

shame) Requires awareness on your part of others’ opinions

of your action

Burnett S, et al. J Cogn Neurosci 2009;21:1736-1750Burnett S, Blakemore S-J. Ann NY Acad Sci 2008;1167:51-56

Processing EmotionsAdolescents activate more of the medial

prefrontal cortexExperiencing social emotions is different

in adolescentsPerhaps adolescents are still “working out”

social situationsLess efficient and automatic

Burnett S, et al. J Cogn Neurosci 2009;21:1736-1750Burnett S, Blakemore S-J. Ann NY Acad Sci 2008;1167:51-56

How Not to Embarrass a Teen1

Don’t correct or reprimand her in front of others.

Don’t fix his clothes, straighten his tie, or tuck in his shirt in public.

Don’t call her by a pet nickname in front of her friends.

Don’t kiss, hug, or show affection on school grounds.

Don’t run into the middle of class to bring something he’s forgotten.

1Elias Z, Goldman T. How Not to Embarrass Your Kids: 250 Don’ts for Parents of Teens.New York, NY: Warner Books; 2009

ConclusionsAdolescents see and react to the world

differently than children or adultsLate maturation of areas of the brain responsible

for complex thought processes helps explain Delayed psychosocial maturationAdolescent behavior (including involvement in

risky endeavors)Adolescents need supportive parents, adults, and

institutions that provide guidance and help them learn appropriate skills and adult behaviors

ImplicationsHealth promotionPublic policy

Tobacco Use9.4% of high school students use cigarettes

frequently (>20 of 30 days/month)1

Half of the 3000 adolescents who begin smoking each day will become daily smokers2

90% of adult smokers began smoking as adolescents2

1Centers for Disease Control and Prevention. Youth Risk Behavior Surveillance. http://www.cdc.gov/mmwr/PDF/SS/SS5505.pdf2Ziedonis D, et al. Adolesc Med Clin 2006;17:381-410

Preventing Tobacco UseStandard approach:

Advise adolescent of adverse effects of tobacco use

Developmentally appropriate approach:Parental supervisionPolicy making:

Prohibiting sale of tobacco to minors

Prohibit tobacco advertising

Prohibit tobacco use on school grounds (students, staff, parents)

Preventing Tobacco Use3834 youths 12-17 years interviewed 3 times

over a 4-year periodOdds of progressing from experimentation

to established smoking reduced by 40% in towns with strong restaurant smoking regulations9.6% risk in towns with weak regulations vs. 7.9%

for towns with strong regulations Rationale:

Reduce youths’ exposure to tobacco in public places (lowers perception of smoking prevalence)

Change perceived social acceptability of smokingSiegal M, et al. Arch Pediatr Adolesc Med 2008;162:477-483

Brain Development and PolicyRoper v. Simmons (2005, US Supreme Court)

17-year-old convicted of murder and sentenced to death American Psychological Association (APA) and AMA filed

briefs arguing that adolescents’ still developing brains made them different than adults. Death penalty was outlawed if offender <18 years of age when crime committed.

Hodgson v. Minnesota (1990, US Supreme Court)Case challenged Minnesota law requiring parental

consent for abortion. The APA argued that by age 14 or 15 years, adolescent decision making was essentially equivalent to that of an adult.

Johnson SB, et al. J Adolesc Health 2009;45:216-221