Effects of Drugs of Abuse on the Developing Brain

Ken Winters, Ph.D.

Collaborating Investigator, Treatment Research Institute

Professor, Department of Psychiatry, University of Minnesota

winte001@umn.edu

The Downtown Club of Philadelphia, November 23, 2004

Overview

•Scientific study of brain development can help us understand adolescent behavior•risk-taking and poor judgment•vulnerability to drug abuse

•Relevance to parenting, prevention and treatment

Keep in mind…..•The research on neuro-

development is in the early stages

•Many key human studies on youth can not be conducted because of ethical considerations

Suggested Readings• www.thebrain.mcgill.ca/flash/index_d.html#

Dubuc, B. (2004). The brain from top to bottom

• www.drugabuse.gov/Published_Articles/Leshner A. (2000). Oops. How casual drug use leads to addiction. National

Institute on Drug Abuse, September, 2000.

• Why do they act that way? : A survival guide to the adolescent brain for you and your teenWalsh, D. (2004). NY: Simon & Schuster.

• What makes teens tick?Wallis, C. (May 10, 2004). NY: Time magazine.

• The adolescent brain and college drinker: Biological basis of propensity to use and misuse alcohol. Spear, L. (2002). Journal of Studies on Alcohol, 14, pp. 71-81.

Some Background

What is adolescence?

Grade Alcohol % Marijuana % Any Illicit %

8 20 8 10

10 35 18 21

12 49 22 25

Substance Use by Youth - Prior Month 2002

(Monitoring the Futures, 2003)

Substance Abuse/Dependence rates vary:

3-15%

Can Addiction be Prevented by Delaying Drug Use Onset?

•Every year use of a substance is delayed, the risk of developing a substance use disorder is reduced.

Percentages of Past Year Alcohol Dependence or Abuse Among Adults Aged 21 or Older, by Age of First Use (SAMHSA, 2004)

1615

9

4.22.6

0

5

10

15

20

<12 yrs 12-14 yrs 15-17 yrs 18-20 yrs 21+ yrs

Age Started Drinking

Perc

en

t

Adolescence is a period of profound brain maturation. It was believed that

brain development was complete during childhood

The maturation process is not complete until about age 24!!!

• During late childhood, neurons get bushier and increase in the number of connections.

• At about age 11 in girls and age 12½ in boys, this thickening undergoes pruning.

• At the same time, the myelin sheaths that encase nerve cells thicken.• Myelin sheaths are like insulation on a wire; they

make nerve cell transmissions faster and more efficient

• Net effect when complete is faster, yet fewer, connections in the brain.

Construction Ahead

Construction Ahead

motivation

emotion

judgment

cerebellum

amygdala

nucleus accumbens

Pruning occurs in stages, from back of the brain to the front

prefontal cortex

physical coordination; sensory processing;

motivationemotionjudgment

Age 24

physical coordination; sensory processing;

• Back of brain matures before to the front of the brain…• sensory and physical activities

favored over complex, cognitive-demanding activities

• propensity toward risky, impulsive behaviors • group setting may promote risk taking

• poor planning and judgment

Arrested Development

• Back of brain matures before to the front of the brain…• activities with high excitement and

low effort are preferred• poor modulation of emotions (hot

emotions more common than cold emotions)

• heightened interest in novel stimuli

Arrested Development

• Neurodevelopment likely contributes to…. • > risk taking (particularly in

groups)

• > propensity toward low effort - high excitement activities

• > interest in novel stimuli

• < capacity for good judgment & weighing consequences

Are adolescents more susceptible to alcohol than adults?

• Adult studies suggest that the areas of the adolescent brain that are remodeled are sensitive to the effects of alcohol

• Four pieces of evidence

Are adolescents more susceptible to alcohol than

adults?

1. Adolescent rats are less sensitive to the sedative and motor impairment effects of intoxication

Supporting Human Studies

1. Reduced sensitivity to intoxication

Current (Past Year) Adults1 17-202 18-193

Alcohol Dependence 7.2 14.6 10.5

1 NRC Report, 1999

2 NY State Household, 1993 3 MN Student Survey, 1995

Comparison of Alcohol Dependence Rates

Survey Data Suggest that Adolescents Are Less Sensitive to Alcohol’s Effects

148

26 2430 32

0

20

40

60

80

100

8th Graders 10th Graders 12th Graders

5+ drinks in row, past 2 weeks

Been drunk past month

Monitoring the Future, 2001

Are adolescents more susceptible to alcohol than

adults?

2. Adolescent rats are more sensitive to the social disinhibition induced by alcohol use

Wanna lookfor some cheese

with me?

Sure!

Are adolescents more susceptible to alcohol than adults?

3. Adolescent drunk rats perform worse on memory tasks than adult drunk rats

Ugh??

disrupts the hippocampus

brain damage in the PFC

converts informatio

n to memory

planned

thinking

Supporting Human Studies

3. Greater adverse effects to cognitive functioning

Alcohol’s Effects

• Adolescents with a history of extensive alcohol use, compared to a control group….

Reduced hippocampus volume (10-35%)

Less brain activity during memory tasks

(Brown, 2002; Wuethrich, 2001)

Are adolescents more susceptible to alcohol than

adults?

4. Hyperexcitability issue

• Alcohol relieves hyperexcitability state

• Relief is temporary; continued seeking of alcohol is reinforced

• Hyperexcitability is a key characteristic of conduct disorder, ODD and ADHD, which are often co-morbid with alcohol use disorders

• Hyperexcitability….• may have its origins in neurological deficits• found in non-alcoholic relatives - suggests

inheritance of this trait

ADHD

ODD

Con Dis

Sub Use Dis

Are adolescents more susceptible to alcohol than adults?

1. Reduced sensitivity to intoxication

2. Increased sensitivity to social disinhibitions

4. Medicates “hyperexcitability”

Increases reinforcing properties

Are adolescents more susceptible to alcohol than adults?

Greater deficits

3 Greater adverse effects to cognitive functioning

• Neurodevelopment likely contributes to…. • > risk taking (particularly in

groups)

• > propensity toward low effort - high excitement activities

• > interest in novel stimuli

• < capacity for good judgment & weighing consequences

Implications of this new science:

Enhancing parenting, prevention and treatment

1. Will parents, health service providers and young people benefit by this knowledge about basic principles of brain development?

• The developing brain’s software does not include program language that says “on second thought”

Implications of this new science:

Enhancing parenting, prevention and treatment

1. Will young people benefit by learning about basic principles of brain development?

2. Will young people be influenced by the science that suggests drug use has a deleterious effect on the developing brain?

Going beyond “this is your brain on drugs”

THANK YOU!winte001@umn.edu