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Gateway Disorder?: Kids with ADHD Show Higher Risk for Later Substance Abuse Problems

Two recent large studies reflect growing evidence that ADHD increases children's risk for abusing tobacco, alcohol and other drugs when they are older. It remains a mystery whether the link is causal



Dream in the Dark of Day, Flickr

One of the top worries for parents of kids with attention-deficit hyperactivity disorder (ADHD) is the long-term consequences of this condition. "Families want to know, 'So what does this mean?'" says Alice Charach, head of the neuropsychiatry team at The Hospital for Sick Children in Toronto.

Two recent, large reviews of previous studies reveal one disquieting answer: Getting an ADHD diagnosis in childhood is associated with nicotine and alcohol dependence in adulthood.

The two studies' results on marijuana and other drugs, however, were more mixed. One review—a meta-analysis published in the April issue of Clinical Psychology Review by a team of researchers at the University of California, Los Angeles, (U.C.L.A.) and the University of South Carolina, Columbia—concluded that children with ADHD also have a strong risk of abusing marijuana, cocaine and other unspecified drugs.

In contrast, Charach's team—which published its review in the January issue of the Journal of the American Academy of Child & Adolescent Psychiatry—also found an increased risk for marijuana and other drugs, but decided the results of the individual studies examined were too varied to reach a strong conclusion. Overall, however, "the similarities outweigh the differences" between the two meta-analyses, Charach says. Steve Lee, lead researcher on the U.C.L.A. review, agrees, "I think both studies are collectively persuasive."

Charach's study included 2,000 participants in a nicotine use analysis and 3,200 participants an alcohol abuse review. And 5,400 subjects were involved in the U.C.L.A. team's nicotine dependence analysis, whereas more than 2,500 participants were the focus in their alcohol abuse analysis. Ten of the studies appeared in both reviews, resulting in an overlap of 2,000 patients.

Knowing the connections among substance abuse problems and ADHD—a disorder in which patients are unable to focus on tasks and fail to control their impulses as well as others of their age groups do—means doctors and parents can get an early start on preventing abuse. Parents can carefully monitor where their kids are, what they're doing, and who they're friends with, experts say. Of course, that's standard advice for all parents, but Lee emphasizes that parents of ADHD children need to be more consistent in their monitoring and in providing rewards and consequences. "You have a lot less wiggle room," he says. That can be difficult, and parents may need support from a mental health professional, he adds.

Charach agrees that children with ADHD need extra support and guidance. She suggests plenty of supervised activities outside of school. "Find something they excel in," she says. Children with ADHD often have trouble making friends and structured activities give them more chances to meet other kids.

Parents can also start talking to their kids early about making good choices. Whereas most children do not start experimenting with drugs until adolescence, parents should initiate discussions about substance abuse when their children are in fifth or sixth grade, says Timothy Wilens, a Harvard Medical School psychiatrist who was not involved in the studies. Doctors can even show older children with the disorder the research on their higher risk for addiction. Wilens says he tells his college-age patients, "Look, you've got ADHD, you've got to be careful." He adds, "Kids hear that."

Experts are optimistic about the impact parents and doctors can have. "I think we've got a very, very good chance at interrupting" the "chain of events" that lead from childhood ADHD to later substance abuse, Lee says.

Scientists think ADHD and substance abuse may arise from a common pathway in the brain because both disorders are associated with dopamine, a chemical messenger that controls movement, emotions and feelings of pleasure and pain. "How efficiently [dopamine is] transported in the brain seems to be disrupted in ADHD as well as in drug abuse," Lee says. But scientists still don't know the exact mechanism of this relationship. "They're still trying to parcel out the neurobiology," Wilens notes.

Lacking the details of this biology, researchers cannot say if ADHD and substance abuse are directly linked. The actual link may be another syndrome, called conduct disorder, some researchers say. Psychiatrists characterize this condition as chronic problems with criminal activity and defiant, or antisocial, behavior. ADHD and conduct disorder are often found together—27 percent of ADHD children also have conduct disorder, according to a study in the February issue of Pediatrics.

Along these lines David Brook, a psychiatrist at New York University Langone Medical Center, has published two studies that found conduct disorder is the direct predictor of substance abuse. David Fergusson, a psychologist at the University of Otago, Christchurch, in New Zealand, has found that kids who have ADHD but not conduct disorder do not go on to develop substance abuse problems. "Conduct disorder is a mediator between earlier ADHD and later substance use disorder," Brook says.

Charach and Lee agree that conduct disorder may be a mediating factor, but they say that they could not provide a statistical analysis of the relationship because few studies have differentiated between subjects having only ADHD and those with both disorders.

But maybe it does not matter exactly how ADHD appears to lead to substance abuse in later life. "The arguments are becoming theoretical," says Fergusson, who thinks substance abuse in people with ADHD is "likely" due to conduct disorder. "Really, our major concerns now need to be with developing treatments."

Although doctors and researchers think close monitoring can prevent drug abuse in ADHD kids, treating sufferers who already have substance use problems is more challenging. So far, scientists have not found an effective treatment. One small study treated amphetamine-dependent, ADHD adults with sustained-release methylphenidate, a mild stimulant commercially sold as Ritalin-SR. The 12 study participants who took Ritalin-SR did not reduce their ADHD symptoms nor their drug dependence more than the 12 participants who took a placebo, according to results published in the April 2010 issue of Drug and Alcohol Dependence. A larger study administered osmotic-release oral-system methylphenidate, commercially sold as Concerta, to adult smokers with ADHD. The drug helped the 204 study participants control their ADHD symptoms but not their smoking, according to a paper published in the December 2010 issue of the Journal of Clinical Psychology.

It may turn out that seeing a therapist is more effective than drug treatment. Cognitive behavioral therapy, a particular type of talk therapy, works for both ADHD and substance abuse in adolescents and adults, Harvard's Wilens says. It has not, however, been studied as a treatment for people with both disorders.

So, what is the best treatment for adult addicts with ADHD? How should clinicians respond to ADHD kids who are just starting to experiment with drugs? Says Wilens, "This affects a lot of kids, and we really don't have answers to these important questions."

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