Adolescent Brain Development

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Adolescent Brain Development

• Sara Salek, M.D.
• Medical Director for Childrens Services
• Division of Behavioral Health Services
• Arizona Department of Health Services

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• We now know through science that the first
  three years of life is the most critical time
  period. It is the time period when the brain
  develops at a greater rate than any time during
  the course of a persons life.but by age 10 your
  brain is cooked and theres nothing much you can
  do.
• Rob Reiner, National Governors Association
  Speech Feb 97

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Goals of Presentation

• Discuss basic brain anatomy and function
• Provide overview on brain development in humans
• Describe our current understanding of adolescent
  phase of brain development
  
• Review concerns about alcohol use in the
  adolescent phase of brain development
  

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Introduction The Human Brain

• The most complex three pound mass in the known
  universe
  
• At fours weeks gestation, neurons are forming at
  250,000 per minute
  
• ? 90 of its adult size by age 6
• The average adult brain contains around 100
  billion neurons
  

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Prefrontal Cortex

• CEO of the brain
• Memory
• Voluntary Motor Control
• Attention
• Reasoning
• Planning
• Decision Making
• Impulse Control
• Abstract Thinking

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Gray vs. White Brain Matter

• Gray Matter
• Neurons cell bodies and dendrites
• Thinking portion of brain
• White Matter
• Insulation for neurons myelination
• Enhances efficiency

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Brain Development

• 3-4 weeks gestation
• Key events in CNS development
• Fold of ectodermal tissue into neural tube
• 4-12 weeks gestation
• Neural tube becomes different parts of nervous
  system
  
• Forebrain and spinal cord develop

Source Lenroot RK. Giedd JN. Brain development
in children and adolescents insights from
anatomical magnetic resonance imaging. Review
94 refs Neuroscience Biobehavioral Reviews.
30(6)718-29, 2006.
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Brain Development

• 12-20 weeks gestation
• Neurons multiply and migrate
• 15 weeks gestation
• Surface of brain begins to fold into sulci and
  gyri

Source Lenroot RK. Giedd JN. Brain development
in children and adolescents insights from
anatomical magnetic resonance imaging. Review
94 refs Neuroscience Biobehavioral Reviews.
30(6)718-29, 2006
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Brain Development

• 20 weeks gestation
• Proliferation and organization of synapses
• 24 weeks gestation to 4 weeks after birth
• Rapid cell death

Source Lenroot RK. Giedd JN. Brain development
in children and adolescents insights from
anatomical magnetic resonance imaging. Review
94 refs Neuroscience Biobehavioral Reviews.
30(6)718-29, 2006
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Critical Periods

• Window of time in which brain must receive
  certain type of stimuli to develop optimally
  
• Examples in humans
• Vision
• Hearing

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Introduction Adolescence

• Interplay of changes
• Emotions
• Hormones
• Physical Body
• Judgment

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Adolescence Definition

• Transition from childhood to adulthood
• No fixed age range
• Individual acquires skills necessary to survive
  on own
  

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Adolescence Behavior

• Behavior characterizing adolescence
• Increased risk-taking and novelty seeking

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Adolescence Puberty

• Puberty sexual maturation process that occurs
  during adolescent period
  
• Puberty ? Adolescence
• Girls begin puberty 1-2 years before boys

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Adolescence Puberty

• Hormonal Change
• Hypothalamic-Pituitary-Gonadal Axis
• Gonadotropin-releasing hormone from hypothalamus
• FSH and LH from pituitary gland
• Estrogen and testosterone from ovary
• Testosterone from testis

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Adolescence Societal View

• Societal Limitations
• Consume Alcohol
• Marriage
• Vote
• Join military

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Adolescence Brain Development

• Unique Process
• Neuronal circuitry changing
• Discoveries made possible by advanced brain
  imaging technology

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Imaging in Children/Adolescents

• Studies previously limited CT scans and x-rays
  exposed children to ionizing radiation
  
• Magnetic Resonance Imaging (MRI)
• Non-ionizing radiation
• Provides detailed images of brain

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MRI Studies of Brain Development

• 1980s
• First MRI studies of brain development
• 1990s
• General findings white matter increases and gray
  matter decreases

Source Lenroot RK. Giedd JN. Brain development
in children and adolescents insights from
anatomical magnetic resonance imaging. Review
94 refs Neuroscience Biobehavioral Reviews.
30(6)718-29, 2006.
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Adolescent Brain Development NIMH Study

• First large scale longitudinal study
• NIMH Child Psychiatry Branch 1989
• Scans children/adolescents at 2 y intervals
• Dec 05 4000 scans from 2000 subjects

Source Lenroot RK. Giedd JN. Brain development
in children and adolescents insights from
anatomical magnetic resonance imaging. Review
94 refs Neuroscience Biobehavioral Reviews.
30(6)718-29, 2006.
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Adolescent Brain Development NIMH Study

• Three goals of study
• Map developmental trajectories of brain
  development
  
• Differentiate genetic vs. environmental
  influences
  
• Use results of study to guide treatment or
  optimize healthy brain development
  

Source Lenroot RK. Giedd JN. Brain development
in children and adolescents insights from
anatomical magnetic resonance imaging. Review
94 refs Neuroscience Biobehavioral Reviews.
30(6)718-29, 2006.
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Adolescent Brain Development

• Dr. Giedd et al. 1999
• Longitudinal study on 145 children/adolescents
• Two waves of gray matter
• over-production
• Conception to 18 months
• Adolescent period

Source Giedd JN, Blumenthal J, Jeffries NO, et
al. Brain development during childhood and
adolescence a longitudinal MRI study. Nature
Neuroscience, 1999 2(10) 861-3.
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Adolescent Brain Development

• Increased cortical gray matter
• Extra connections between neurons arborization
• Maximum thickness at different times

Source Lenroot RK. Giedd JN, Blumenthal J,
Jeffries NO, et al. Brain development during
childhood and adolescence a longitudinal MRI
study. Nature Neuroscience, 1999 2(10) 861-3.
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Adolescent Brain Development

• Late development of prefrontal cortex
• Gray matter loss occurs latest in the
  dorsolateral prefrontal cortex (DLPFC)
  
• Reaches adult levels 20s
• Portion of brain involved in higher order
  cognitive functions
  

Source Giedd JN. Structural Magnetic Resonance
Imaging of the Adolescent Brain. Ann. N.Y. Acad.
Sci. 2004 1021 77-85
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Adolescent Brain Development

• Sowell et al. 1999
• Compared brain MRI scans of 23-30 year olds to
  12-16 year olds
  
• Areas of frontal lobe showed the largest
  differences among these two groups
  

Source Teenage Brain A work in progress
available at www.nimh.gov
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• Increased Gray Matter
• Decreased Gray Matter
• More Efficient Connections

Pruning
Genetics
Environment
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Example of Genes vs. Environment

• Cerebellum and corpus callosum studies in twins
• Corpus callosum very similar (genetics)
• Cerebellum different (environment)

Source Interview with Jay Giedd, Inside the
Teenage Brain, Frontline PBS, available at
www.pbs.org
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Alcohol Use in Adolescence

• Alcohol kills ? 6.5 times more individuals under
  age 21 than all other drugs combined (The
  National Institute of Alcoholism and Alcohol
  Abuse)
• ? 25 of all underage drinkers meet the criteria
  for abuse or dependence (The National Center on
  Addiction and Substance Abuse at Columbia
  University)

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Arizona Youth Survey 2006Arizona Criminal
Justice Commission

• Average age of first alcohol use 12.84 vs.
  regular alcohol use 14.21
  
• Reduction in alcohol use in all grades compared
  to 2004 survey
  
• Decreased 1.5 to 3.4 in each grade for lifetime
• Decreased 1.2 to 4.1 in each grade for 30 day

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Adolescence and Drug Use

• Different response to alcohol during this
  developmental period
  
• Sensitivity to rewards different than adults
• Frontal lobe developing at a time when humans
  most likely to experiment with drugs
  

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Rat Studies

• Compared to adults, adolescents experienced
• Increased brain damage after 4 day binge drinking
  
  
• Increased memory impairment
• Less sedation
• Less motor impairment

Source Aaron White, Rethinking underage drinking
-- What does science have to say about it?
www.science-says.com, Nov 2006
32
Human Studies

• Tapert et al., 2002
• Neuropsychological functioning and substance use
  involvement over 8 year period in 16-24 yo
  
• Cumulative levels of alcohol and other drug use
  correlated with impairments in verbal learning
  and memory
  
• Heavy drinking was associated with attention
  deficits
  
• Experiencing withdrawal from alcohol predicted
  visuospatial deficits

Source Tapert SF. Granholm E. Leedy NG. Brown
SA. Substance use and withdrawal
neuropsychological functioning over 8 years in
youth. Journal of the International
Neuropsychological Society. 8(7)873-83, 2002
Nov.
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Human Studies

• De Bellis et al., 2000
• Hippocampus smaller in adolescents who abused
  alcohol
  
• Amount of hippocampal damage correlated with the
  number of years of alcohol abuse

Source De Bellis MD. Clark DB. Beers SR. Soloff
PH. Boring AM. Hall J. Kersh A. Keshavan MS.
Hippocampal volume in adolescent-onset alcohol
use disorders.see comment. American Journal of
Psychiatry. 157(5)737-44, 2000 May.
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Adolescent Drinking Risk and Protective Factors

• Risk Factors
• Family History
• Peer alcohol use
• Temperament and personality
• Childhood behavior problems
• Family factors

• Protective Factors
• Temperament
• Religiosity
• Parenting factors

Source Windle M. Spear LP. Fuligni AJ. Angold A.
Brown JD. Pine D. Smith GT. Giedd J. Dahl RE.
Transitions into underage and problem drinking
developmental processes and mechanisms between 10
and 15 years of age. Review 143 refs
Pediatrics. 121 Suppl 4S273-89, 2008 Apr.
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Cautionary Statements

• It is essential to balance the excitement about
  all the new learning with caution about the
  limits of understanding
  
• Jack Shonkoff, interview for Inside the teenage
  brain for PBS frontline
  
• Direct correlations between adolescent brain and
  behavior changes has not yet been established

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Summary

• Brain development begins in early gestation and
  continues into twenties
  
• Major brain restructuring during adolescence
  includes prefrontal cortex, which is important in
  executive functioning
  
• Alcohol use during adolescence concerning given
  ongoing brain development
  
• More longitudinal studies needed to confirm
  preliminary data