from Psychology Today

by Professor Gary L. Wenk Ph.D

Addicted to drugs? blame it on brain anatomy


Do you feel impulsive today? How much risk are you willing to expose yourself to for the sake of a few dollars; how far are you willing to exceed the speed limit just to cutting off a few minutes from the morning commute; how easy is it for you to turn down just one more line of cocaine?  Each of us would answer these questions with a wide range of nuanced responses. Life is a balancing act: on one side is impulsive action; on the other is thoughtful hesitation.

Psychologists have studied this balance for many decades; cartoonists have depicted the event as an argument between an angel sitting on one shoulder while the devil sits on the other; both are whispering into their respective ear. Do it; don't do it. Our response is significantly influenced by the genes we inherited from our parents. Risk takers give birth to risk takers. The category that you fall into as a child offers insight into your future mental and physical health and your probability of spending time in jail, becoming obese or developing an addiction to cocaine.
Recently, a group of neuroscientists at the University of Cambridge published (Science, Feb 2012) evidence showing that abnormalities in the connections between specific parts of the brain (within the inferior frontal lobe) underlie our ability or inability to control our behavior.  Furthermore, their results provide insight into why siblings sometimes display quite different levels of impulse control.  More importantly, their study offers hope that it is possible to avoid the same fate as your addicted sibling —they're just not sure how, yet.
The scientists examined the brains from fifty biological sibling pairs. Each pair consisted of someone who was dependent upon stimulant drugs (such as methamphetamine or cocaine); the sibling pair was required to have no history of drug or alcohol abuse. The information obtained from these siblings was compared to that obtained from fifty healthy volunteers who were unrelated and matched for age and level of intelligence.
The siblings, whether addicted to stimulants or not, both demonstrated personality traits that are highly predictive of being vulnerable to long term drug abuse. The major behavioral symptom was having poor inhibitory control, i.e. it was quite difficult for them to stop doing something risky when instructed to do so. The scientists discovered a high correlation between an inability to control one's behavior and a deformed structural integrity in brain regions that critical for this ability.
Why is this finding so important? Because it clearly demonstrates that important features of our brain anatomy, features that are present at birth, predispose us to drug addiction. In the past, the assumption was that the drug-taking experience altered the brain and all that was necessary was that we avoid the drug, i.e. "Just Say No."  Essentially, this approach is doomed to failure because we inherit our self-control deficits. The imbalance in control that develops between vulnerable brain regions is also thought to predispose people to thrill-seeking and impulsive behaviors such as gambling.  An explanation for why one sibling succumbed to drug dependence while the other did not remains to be determined.

© Gary L. Wenk, Ph.D. Author of Your Brain on Food (oxford, 2010)