Differences in the networks of brain cells may explain why some teenagers are more susceptible to impulsive risk-taking behavior like smoking or experimenting with drugs, according to a new study.
The study, published in the journal Nature Neuroscience, sheds light on the question of whether certain brain patterns that are characteristic of drug users occur because of the drug use or are the cause of drug use.
Using functional brain imaging of 1,896 14-year-olds, the researchers from the University of Vermont identified seven networks involved when impulses were successfully inhibited and six networks involved when inhibition failed. The teenagers were asked to perform a repetitive task that involved pushing a button on a keyboard, and then asked to stop the act of pushing the button in mid-action. When teenagers were successful at stopping mid-act, the inhibitive networks would light up. Those teens with better inhibitory control were able to succeed at this task faster.
Researchers looked at activity in the "orbitofrontal cortex," a region of the brain associated with experimentation with alcohol, cigarettes and illegal drugs in early adolescence. They found that activity in this region was reduced in those who misused any substance (alcohol, nicotine or illicit substances), even in those who only used alcohol one to four times in their life. This strongly suggests, since one to four uses is unlikely to substantially impair brain functions, that the differences in brain networks were there before the drug use.
"These networks are not working as well for some kids as for others," said University of Vermont researcher Robert Whelan, a co-author of the study. This makes them more impulsive, he said.
The study also found that separate neural networks are involved with the symptoms of attention deficit hyperactivity disorder (ADHD). These ADHD networks are distinct from those associated with early drug use.
This is an important finding because there has been some concern that having ADHD puts someone at risk for substance abuse. But this study shows that these similar impulse issues are regulated by different networks in the brain, suggesting that ADHD is not necessarily a full-blown risk for drug use as some other recent studies suggested.
Though adolescence is a time to push boundaries and take risks, for teens who are pre-wired to have poor impulse control, it may lead to dangerous or harmful behavior. Some studies have shown that early educational interventions focusing on improving cognitive control are effective in improving impulse control. For example, one type of training, called PATHS (Promoting Alternative Thinking Strategies) teaches children, when they get upset, to stop, take a deep breath, say what the problem is and how they feel, and construct an action plan. After this type of training, children had better inhibitory control.
Laurie Tarkan is an award-winning health journalist whose work appears in the New York Times, among other national magazines and websites. She has authored several health books, including "Perfect Hormone Balance for Fertility." Follow her on Twitter and Facebook.