SUNDAY, April 29 (HealthDay News) -- Teens with
attention-deficit/hyperactivity disorder (ADHD) and teens who start
using cigarettes, drugs or alcohol tend to share at least one
personality trait: impulsiveness, experts say.
But a new brain-imaging study of nearly 1,900 14-year-olds finds
that the brain networks associated with impulsivity in teens with
ADHD are different compared to those who use drugs or alcohol.
What that finding suggests is that multiple underlying
mechanisms drive impulsivity -- in other words, the impulsivity
that leads kids to blow off their homework and the impulsiveness
that drives kids to take a drag off a joint aren't the same,
"The behavior of the two groups might look the same, but it's driven by different brain networks," said lead study author Robert Whelan, a postdoctoral research fellow at the University of Vermont.
Moreover, the findings, published in the April 29 online issue
Nature Neuroscience, could suggest that the brain is primed to push some teens -- but not others -- toward substance abuse.
ADHD is a neurobehavioral disorder marked by excessive levels of
activity, inattention and impulsiveness beyond what's normal for a
People with ADHD are at higher risk of substance abuse and
alcoholism. The explanation was thought to lie in the lack of
self-control or inability to curb impulses that are part of the
disorder, Whelan said.
But the brain-imaging study suggests that from a neurological
standpoint, ADHD and substance use may not be nearly as closely
tied as previously believed, Whelan said.
In the study, researchers used data from an ongoing study of
European teens who underwent brain imagining tests every two years
starting at age 14. The youths were asked about symptoms of ADHD
and if they had tried alcohol, cigarettes or other drugs.
While having their brains scanned, the students took a test used
to measure self-control, or inhibition: Participants were told to
press a button when they saw a right or a left arrow flash on a
screen, but not to press the button when the arrow pointed up.
The kids with ADHD and those who had tried various substances
didn't perform any worse on the test of self-control than other
kids. However, researchers did find distinct patterns of brain
activity in ADHD and in kids who'd tried alcohol, cigarettes or
drugs while taking the test.
Among the kids who had tried alcohol, cigarettes or other drugs
(mostly marijuana), scans showed different patterns of brain
activity in the right inferior frontal gyrus and in the orbital
frontal cortex compared to teens who had abstained. Prior research
has found the inferior frontal gyrus is involved with inhibition.
For example, people with head injuries that damaged that area of
the brain have problems with inhibition, Whelan said, while the
orbital frontal cortex has been implicated in drug use.
Even teens who reported having only tried a drink or two by age
14 showed a different pattern of activity in the orbital frontal
cortex, suggesting the brain differences aren't caused by the
substances, but are already present and play a role in what drives
certain teens to experiment with alcohol and others to abstain,
In the teens who had symptoms of ADHD, different networks lit up
during the self-control test. Kids with ADHD symptoms showed
differences in the bilateral frontal lobe and the basal
"The fact that we found there were different networks lends credence to the argument that ADHD and substance abuse are not so tightly coupled," Whelan said.
Dr. Lukshmi Puttanniah, director of child and adolescent
psychiatry at Lenox Hill Hospital in New York City, said the study
strongly suggests that impulsiveness can have many underlying
"It's adding to a body of knowledge that the fundamental thing underlying both ADHD and substance use is difficulty controlling impulses," Puttanniah said. "Some people thought that whatever neurobiological pathway that underlies it is common between ADHD and substance abuse. But what this study shows is the neurobiological pathways underlying the impulsivity of ADHD and substance use disorders are actually distinct."
U.S. National Institute of Mental Health has more
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
Copyright © EBSCO Publishing. All rights reserved.