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Why Do They Do That? Brain Development During Adolescence

Why Do They Do That? Brain Development During Adolescence. Daniel Krowchuk, M.D. Departments of Pediatrics and Dermatology Wake Forest University School of Medicine. November 15, 2009. “STD Cases Up Among Mississippi Teens” - Youths 15-19 comprise 7.6% of the state’s population

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Why Do They Do That? Brain Development During Adolescence

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  1. Why Do They Do That? Brain Development During Adolescence Daniel Krowchuk, M.D. Departments of Pediatrics and Dermatology Wake Forest University School of Medicine

  2. November 15, 2009 • “STD Cases Up Among • Mississippi Teens” • - Youths 15-19 comprise 7.6% • of the state’s population • In 2008, they accounted for: • 40.1% of chlamydia cases • 32.3% of gonorrhea cases “Merits of Abstinence Education Debated”

  3. 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

  4. The leading cause of death for teenagers in the U.S. is A. AIDS B. cancer C. homicide D. suicide E. unintentional injury

  5. Deaths, Percent of Total Mortality, and Death Rates by Cause, 15-19 year olds, U.S., 2007 Heron M, et al. Pediatrics 2010;125:4-15 (data from National Vital Statistics System: mortality 2007, www.cdc.gov/nchs/nvss/mortality_tables.htm )

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

  7. Lifetime Prevalence of Use (%) of Various Substances by High School Seniors http://monitoringthefuture.org/

  8. Adolescence Physical Development (Puberty) Early Adolescence Middle Adolescence Late Adolescence Social and Emotional Maturation 10 – 13 years 14 – 16 years 17 – 21 years Cognitive Development

  9. 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

  10. 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

  11. 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)

  12. 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 another • 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.

  13. Changes in Brain Anatomy • Pruning • Information that is used regularly 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.

  14. Cortical Development Cells and connections are lost if not used (facilitating more efficient and faster information processing) Cells and connections increase to provide opportunities for leaning and memory http://www.pnas.org/content/suppl/2004/05/13/0402680101.DC1/02680Movie1.mpg Gogtay N, et al. PNAS 2004;101:8174-8179

  15. 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

  16. 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?

  17. 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

  18. 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

  19. 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

  20. 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

  21. Measures hemodynamic response (i.e., change in blood flow) related to neural activity 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 C Ad A Galvan A, et al. J Neurosci 2006;26:6885-6892 Galvan A, et al. Dev Sci 2007;10:F8-F14

  22. 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.

  23. Nicotine and Addiction Centers Non-smoker Light smoker (2-5 cigarettes/ day) Rubinstein ML. Pediatr News 2010;44:28 (Sept. 2010)

  24. “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, consequence-based decision • Social skills training (i.e., role-playing) may be beneficial in moderating “hot” cognitions.

  25. 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

  26. 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

  27. 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 Ekman P, Friesen WV. Pictures of Facial Affect. Palo Alto, CA: Consulting Psychologists Press; 1976 Blakemore S-J. Nat Rev Neurosci 2008;9:267-276

  28. 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

  29. 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

  30. 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

  31. Conclusions MacArthur Foundation Research Network on Adolescent Development and Juvenile Justice. Issue Brief 3: Less guilty by reason of adolescence. September 21, 2006

  32. www.nytimes.com

  33. Transition to Adulthood • Traditionally marked by: • Completing school • Leaving home • Becoming financially independent • Getting married • Having a child • Reaching milestones by age 30 • 1960: 77% of women, 65% of men • 2000: fewer than half of women, 33% of men Henig RM. nytimes.com. August 18, 2010

  34. 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

  35. Implications • Health promotion • Public policy

  36. Tobacco Use • 19.5% of high school students are current smokers (>1 time in past 30 days) and 7.3% 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. (2009) http://www.cdc.gov/HealthyYouth/yrbs/index.htm 2Ziedonis D, et al. Adolesc Med Clin 2006;17:381-410

  37. 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)

  38. 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

  39. 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

  40. Caveats • Don’t over-interpret or over-simplify the information • The field is relatively young and growing at a rapid pace • PubMed search of “brain development” and “adolescence” yields 6,666 papers (11/20/09)

  41. Conclusions • Adolescents see and react to the world differently than children or adults • Changes in brain structure and function occur during adolescence and likely impact behavior

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