The Effects of Drugs and Alcohol on the Adolescent Brain
Overview
Though it has long been known that teenagers are prone to impulsive behavior, to emotional
rather than logical thinking, and to not fully considering the long-term consequences of their
actions, only recently has neuroscience and MRI technology provided an understanding of why.
The teenage brain, it turns out, is a brain still developing. To understand the risks associated with
psychoactive substances in adolescents, it helps to understand that teenagers are not just lessexperienced adults; they are undergoing an important yet challenging developmental stage in
which that are prone to errors of judgment, and sensitive to neurological assault by psychoactive
substances. More than any other age group adolescents are at risk for substance addiction, and
more than any other age group they risk permanent intellectual and emotional damage due to the
effects of drugs.
Normal Adolescent Brain Development
The human brain is sculpted by experience. At birth, the brain contains many more neural
connections than it could possible use, but these connections are unspecialized and undeveloped.
As time passes some connections are strengthened (such as the nerves that process the sight of a
mother’s face or sound of a siblings’ voice) and others are pruned away.
The process of refinement and pruning continues throughout childhood, adolescence, and even
into early adulthood. The most marked development in adolescence is in the brain’s frontal lobe
and outer mantle. The pre-frontal cortex, located in the frontal lobe, executes such skills as
setting priorities, formulating strategies, allocating attention and controlling impulses; the outer
mantle is involved with processing abstract information and understanding rules, laws and codes
of social interaction.
The behaviors that accompany these changes are transparent. Teenagers are notorious for their
obsession with social interaction, for making up social rules and breaking them. As teenagers
grow into young adults they often exhibit a fascination with abstract thinking on topics like
history, culture and media, which demonstrates their growing ability to understand the larger
world. While the teenage brain is in some ways ill equipped to make decisions and choices
without the help of trusted adults, it is perfectly designed for the types of intellectual and social
challenges teenagers most need to master.
Still, development of fully mature complex thinking takes a long time. MRI studies show that the
development of the prefrontal cortex and outer mantle of the brain continues into the early 20s,
and may not be completed until the mid 20s. As the wiring for logical thought is used more and
more over time the connections become more robust, and when this process nears completion,
parts of nerves become coated in a fatty layer called a “myelin sheath.” Like insulation on a wire,
this fatty layer allows the nerve connections to process faster, making rational, reasoned
decision-making quicker and more automatic.
Effects of Drugs on the Developing Brain
There are many ways that psychoactive substances can alter or damage the development of the
adolescent brain. Firstly, psychoactive substances often target and alter function of
neurotransmitters, the chemical messengers that allow nerves to communicate at their junctions.
Interference with neurotransmitters can directly damage fragile developing neural connections.
Secondly, use of these substances alters perception and may interfere with the developing
perceptual skills. And finally, the habits and choices associated with the use of drugs and alcohol
slowly become ingrained in the wiring of the brain. Repeated action becomes habit and the habits
of thought, perception, and reasoning developed in childhood and adolescence can stay with a
person throughout his or her lifetime.
Neurotransmitter Function
Alterations in neurotransmitter function are partially responsible for both the high addiction
potential and the devastating effects of methamphetamines and cocaine. The neurotransmitter
dopamine links the nerves in the outer mantle and prefrontal cortex of the brain and is associated
with the feelings of motivation and reward. When adolescents use the problem solving circuitry
of the brain, they experience feelings of both reward and motivation. Over time teens become
more and more motivated to think through problems, and more likely to develop better solutions
as they refine the neural circuitry associated with these skills.
Methamphetamines and Cocaine are known to cause a flood of dopamine into the brain. This is
one reason for the extreme addiction potential of these drugs: their use is associated with a
tremendous sense of reward. It has been found, though, that cocaine addicts have a blunted
perception for certain types of reward, and it is hypothesized that cocaine, and by extension
methamphetamines, over time override the brain’s ability to sense rewards accurately in day-today interactions. The effects of these drugs can be devastating not only to intellectual
development, but to the very ability of the user to feel satisfaction from life.
Alterations in Perception
Perceptual changes caused by drugs can also have long-term complications for adolescent
development, since adolescent perceptive abilities are not fully mature. For example, MRI
studies show that adults tend to use the frontal lobes, or logical problem solving, to determine
facial expressions while adolescents use the amygdala, an area which normally processes
emotions such as fear and worry. It holds true in many studies that where adults use problem
solving areas of the brain to perceive the world adolescents use the more primitive areas of the
brain more associated with emotions, and self-preservation; it also holds true that adult
perception is generally more accurate.
Marijuana, like all drugs, changes perception. And like most drugs, it engenders perception that
is fearful, emotional, defensive, and often inaccurate. Though the short term addiction potential
of marijuana may be less than other drugs, the long-term impact of chronic marijuana use can be
profound. Determining the feelings and motives of other people is necessary to function as an
adult in society. If marijuana use is chronic or constant enough to hinder perceptual maturation,
an adolescent user may encounter misunderstood failures in school, work, and relationships,
which in turn re-enforce the desire to retreat to drugs.
Habit and the Hard Wiring of the Brain
As self help gurus are quick to point out, if you do something for long enough it becomes
automatic. Nowhere does this wisdom more hold true than in adolescence. Though teens may
change clothes, ideas, friends and hobbies with maddening frequency, they are developing ideas
about themselves, their world and their place in it that will follow them for the rest of their lives.
Adults may spend years trying to create or break even the simplest habit, yet most adults find
that their most profound ideas about themselves and the world were developed in high school or
college. This is because, by age 25 or so the brain is fully developed and building new neural
connections is a much slower process.
Conclusion
Early detection and treatment is essential to heading off the development of substance addiction
in adolescents. Given their brain development, teenagers cannot be expected to understand the
full range of consequences in their choices regarding drugs and alcohol. The disease must be
prevented, and where it cannot be prevented it must be cured while there is still time for a full
recovery.
Information Taken from The Adolescent Brain: A Work in Progress , Daniel R. Weinberger, MD,
Brita Elvevag, PhD, and Jay N. Giedd, MD, for The National Campaign to Prevent Teen
Pregnancy, 2005.
- See more at: http://samafoundation.org/youth-substance-addiction/effects-of-drugs-onadolescent-brain/#sthash.k2GzHny6.dpuf