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Study supports protective effect of stimulant treatment for ADHD
An analysis of all available studies that examine the possible impact of stimulant treatment for attention-deficit hyperactivity disorder (ADHD) on future substance abuse supports the safety of stimulant treatment. Using a statistical technique called meta-analysis, the researchers from Massachusetts General Hospital (MGH) found that medication treatment for children with ADHD resulted in an almost two-fold reduction in the risk of future substance abuse. The report appears in the January 2003 issue of Pediatrics.
"We know that untreated individuals with ADHD are at a significantly increased risk for substance abuse. And we understand why parents often ask whether stimulant medications might lead to future substance abuse among their children," says Timothy Wilens, MD, MGH director of Substance Abuse Services in Pediatric Psychopharmacology, the paper?s lead author. "Now we can reassure parents and other practitioners that treating ADHD actually protects children against alcohol and drug abuse as well as other future problems."
Wilens and his MGH colleagues have conducted previous studies that found a protective effect in stimulant treatment. However, at least one report from another research center asserted that stimulant treatment increased the risk of later substance abuse. In order to resolve the question, Wilens' group searched the medical literature for studies of children, adolescents and adults with ADHD that included followup information on later substance abuse. They identified six such studies conducted in the U.S. and Germany, which provided information on more than a thousand participants with ADHD -- 674 who received stimulant treatment and 360 who were non-medicated -- followed for four years or more. These studies included both the previous MGH research and the study suggesting increased risk.
After application of standard meta-analysis techniques, the researchers found a significant overall reduction in the risk of subsequent substance abuse among those receiving stimulant treatment. They note that four of the six studies showed "striking protective effects of stimulant medications."
Of the other two studies, one did not find significant differences in substance abuse between the treated and untreated groups. Regarding the study that suggested an increased risk, the MGH researchers noted that participants who received stimulant treatment in that study had more problems before they began treatment, particularly a greater incidence of conduct disorder (juvenile delinquency). Since conduct disorder is a recognized and very strong risk factor for substance abuse, it is unclear whether the conduct disorder or the medication actually resulted in the increased substance abuse risk.
The MGH team also noted that the protective effect of stimulant treatment for ADHD in childhood was not as strong in young adults as it was in adolescents. While some of this could relate to the fact that adolescents are still subject to parental supervision, the researchers also suggest that past recommendations that stimulant treatment be discontinued in adolescence could cause the protective effect to disappear in subsequent years.
"From a public health level," Wilens says, "these results finding protection against later substance abuse -- which is one of the most malevolent problems facing adolescents and young adults -- are among the strongest in child psychiatry. Moreover, these findings add to the growing literature supporting the long-term safety of stimulants and other medications for treatment of ADHD."
Wilens and colleagues are continuing to study the biological and psychological mechanisms by which ADHD increases the risk for substance abuse in young people and why treatment decreases the ultimate risk.
Wilens' coauthors are Stephen Farone, PhD; Joseph Biederman, MD, and Samantha Gunawardene, all of the MGH Pediatric Psychopharmacology Unit. The study was entirely supported by grants from the National Institute on Drug Abuse.