The study is published in the Journal of the American Academy of Child & Adolescent Psychiatry.
ADHD is a behavioral disorder characterized by impulsiveness, hyperactivity, and inattention. Some people with ADHD also have conduct disorder, a pattern of disruptive and violent behaviors.
"ADHD increases your risk for cigarette smoking and substance abuse pretty dramatically, and you have to be mindful of that," says study researcher Timothy Wilens, MD, of the Massachusetts General Hospital Pediatric Psychopharmacology Unit and an associate professor of psychiatry at Harvard Medical School in Boston. "If a kid has conduct disorder too, you have to talk about these risks and be careful not to keep extra alcohol and prescription drugs in your medication cabinet."
The onus is on everyone involved. "Parents need to be on top of it and the practitioner does too, and the kid has to own some of it," he says.
Substance Abuse Risk
The researchers examined data from two studies looking at the prevalence of psychiatric and behavioral disorders seen along with ADHD in children. The average age of participants when the study started was about 10, and participants were followed for 10 years. Those study participants diagnosed with ADHD were about 1.5 times more likely to developing substance abuse problems after 10 years, compared with those without ADHD.
Children with persistent ADHD -- or those who still had ADHD after 10 years of follow-up -- were at greater risk for developing substance abuse problems, compared with people who no longer had an ADHD diagnosis after 10 years, the study shows.
People who also had conduct disorder and ADHD had about three times the risk for developing substance abuse problems, compared to those with ADHD alone, the study shows.
The risk of developing a substance abuse problem was not affected by gender, cognitive difficulties, mood disorders, school problems, or family history of substance abuse.
"Boys and girls with ADHD were equal in terms of their risk of developing substance abuse. And academic achievement and cognitive issues did not predict substance abuse at all, so there is probably something else going on," Wilens says.
Role of Medication
The exact role that ADHD treatment, such as stimulant drugs, may play in reducing the risk of substance abuse among people with ADHD is not clear from this study.
The study found that medication treatment did not affect the risk for substance abuse, but more studies would be needed to look at these issues directly to draw any firm conclusions, Wilens says.
Jon Shaw, MD, a professor of psychiatry of the University of Miami School of Medicine, says that these findings mirror what he sees in practice. "This confirms what we know clinically and really replicates previous studies that show us that ADHD is a risk factor for substance abuse later in life."
"It used to be believed that psychostimulants in and of themselves increase the risk for substance abuse among people taking them. But 10 to 15 studies show us that the use of stimulants does not increase this risk," he says.
The increased risk for substance abuse likely has more to do with the nature of ADHD, he says.
"ADHD children are very impulsive and don't learn well from experience and don't respond to the usual contingencies of reward and punishment," Shaw says. "If they have the impulse, they have the proclivity to act on it."
In addition, he says, "many people with ADHD may be self-medicating with marijuana and other substances to mitigate their own inner restlessness and turmoil."
Treating ADHD is essential, Shaw says. "ADHD leads to academic problems and children with untreated ADHD often become targets of teachers who find them disruptive, and it cascades downhill from there."
Stephen Grcevich, MD, a child and adolescent psychiatrist at Family Center by the Falls in Chagrin Falls, Ohio, says that adults with ADHD should be watched closely for signs of substance abuse.
"Kids who were identified as having symptoms of ADHD and conduct disorder should be watched carefully as there may be a role for primary prevention and/or early intervention in terms of substance abuse," he says.