Transcript Slide 1

Daniel Krowchuk, M.D.
Departments of Pediatrics and Dermatology
Wake Forest University School of Medicine
Objectives
 Describe changes in brain structure and function that
occur during adolescence
 Discuss 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.
is
A. AIDS
B. cancer
C. homicide
D. suicide
E. 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
Homicide
6,825
49.8
32.9
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
-
-
-
63.2
62.3
58.1
56.4
55.1
54.7
71.0
68.8
64.4
64.2
62.5
53.7
47.1
47.1
44.7
Been drunk
Cigarettes
http://monitoringthefuture.org/ (1/09)
Adolescence
Physical Development (Puberty)
Early
Adolescence
Middle
Adolescence
Late
Adolescence
Social and Emotional Maturation
10 – 13 years
14 – 16 years
Cognitive Development
17 – 21 years
Social and Emotional Maturation
 Emotional separation from parents
 Develop a sense of personal identity and self-image
 Identify with a peer group
 Explore romantic relationships
Hazen E, et al. Pediatr Rev 2008;29:161-168
Cognitive Development
 Increased ability to think abstractly
 Greater impulse control
 Improved ability to assess risk vs. reward
 Improved use of working memory (the information in
memory available for working on a problem)
Cognitive alterations are associated with
changes in brain structure and function
Hazen E, et al. Pediatr Rev 2008;29:161-168
Casey BJ. Ann NY Acad Sci 2008;1124:111-126
Neuroanatomy Review
 Gray matter (cerebral cortex):
 Contains nerve cell bodies
 Processes and routes information
 Increases 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 Anatomy
 Each new experience results in new connections
between neurons
 By the end of adolescence, the brain contains
 10 - 100 billion neurons

Forming 100 trillion connections with one other
 100 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 Anatomy
 Pruning
 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.
Brain Development and Risk Taking
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 groups
 Substance use
 Reckless driving
 Crimes
 Are adolescents more susceptible to the influences of
risk-prone peers?
Risky Business – The Role of Peers
 Risky decision-making
asessed in:
 106 adolescents (13-16 yrs)
 105 youths (18-22 yrs)
 95 adults (>24 yrs)
 Decision-making assessed
using video game
 Alone
 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 Scale
 5 hypothetical scenarios
 Having sex without a condom
 Riding in a car driven by someone who has been
drinking
 Trying a new drug one knows nothing about
 Breaking into store to steal something one wants
 Driving 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 Peers
 Younger individuals:
 Allowed car to move further after yellow light
 Chose riskier course of action on questionnaire
 Were more likely to be affected by peer influences
Gardner M, Steinberg L. Dev Psychol 2005;41:625-635
Risk-Reward and Brain Activity
 Nucleus accumbens
 Component of the limbic system
 Involved 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 Activity
 Functional MRI performed during tasks weighing
risk and reward
 Adolescents activate the nucleus accumbens more
than adults
 Nucleus 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
Galvan A, et al. J Neurosci 2006;26:6885-6892
Galvan A, et al. Dev Sci 2007;10:F8-F14
Ad
Substance Use and the Brain
 Limbic system - prefrontal cortex connections
grow into early adulthood.
 Certain of these neurons use dopamine to relay
messages
 These 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 situation
 Adolescent surrounded by peers in a stimulating
environment may make an emotionally-based decision
 “Cold” cognition
 Decision made in a calmer, quieter environment
 Adolescent may make a more intellectual, consequencebased decision
 Social skills training (i.e., role-playing) may be
beneficial in moderating “hot” cognitions.
Recognizing Emotions
 Adolescents often misinterpret body language and
words that are spoken
 A 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 Emotions
 Complex network of brain regions involved in
recognizing
 Basic emotions (fear)
 Social emotions (guilt, embarrassment, shame)
 Network includes:
 Amygdala
 Medial prefrontal cortex
 Anterior insula
 Superior 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 face
 All adults correctly interpreted the emotion as fear
 Half of adolescents thought that the woman
expressed shock or surprise
Blakemore S-J. Nat Rev Neurosci 2008;9:267-276
Processing Emotions
 19 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;21:1736-1750
Burnett S, Blakemore S-J. Ann NY Acad Sci 2008;1167:51-56
Processing Emotions
 Adolescents activate more of the medial
prefrontal cortex
 Experiencing social emotions is different in
adolescents
 Perhaps adolescents are still “working out” social
situations
 Less efficient and automatic
Burnett S, et al. J Cogn Neurosci 2009;21:1736-1750
Burnett 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
Conclusions
 Adolescents see and react to the world differently than
children or adults
 Late maturation of areas of the brain responsible for
complex thought processes helps explain
 Delayed psychosocial maturation
 Adolescent 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
Implications
 Health promotion
 Public policy
Tobacco Use
 9.4% 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.pdf
2Ziedonis D, et al. Adolesc Med Clin 2006;17:381-410
Preventing Tobacco Use
 Standard approach:
 Advise adolescent of
adverse effects of
tobacco use
 Developmentally
appropriate approach:
 Parental supervision
 Policy making:
 Prohibiting sale of tobacco
to minors
 Prohibit tobacco
advertising
 Prohibit tobacco use on
school grounds (students,
staff, parents)
Preventing Tobacco Use
 3834 youths 12-17 years interviewed 3 times over a
4-year period
 Odds of progressing from experimentation to
established smoking reduced by 40% in towns
with strong restaurant smoking regulations
 9.6% 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 smoking
Siegal M, et al. Arch Pediatr Adolesc Med 2008;162:477-483
Brain Development and Policy
 Roper 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