Stimulants have long been prescribed to children diagnosed with attention-deficit hyperactivity disorder, or ADHD. Over the past decade, child psychiatrists have debated the long-term potential for these medications to trigger drug abuse. Two new studies indicate that the stimulants do not increase children's risk of abusing cocaine, nicotine, and other drugs as adults.

Although these findings come as a relief to child psychiatrists, not all the news is good. The new investigations, already published online and slated to appear in the May American Journal of Psychiatry, underscore earlier evidence that youngsters with ADHD frequently become drug abusers, whether or not they take prescribed stimulants.

"It is still critical that young people with ADHD be screened for substance abuse," says Nora D. Volkow, director of the National Institute on Drug Abuse in Bethesda, Md.

Boys with ADHD who start stimulant treatment early, at age 6 or 7, face a lower risk of later drug abuse than do those who begin taking medication later, between ages 8 and 12, report psychologist Salvatore Mannuzza of New York University's Child Study Center and his colleagues.

In the 17-year study, 27 percent of early-treated participants abused drugs by their mid-20s. That roughly equaled the drug abuse rate among young men who had never had any psychiatric ailments.

In contrast, 44 percent of late-treated boys became drug abusers by young adulthood, a rate comparable to earlier estimates for ADHD kids regardless of their treatment. Most of these late-treated children were diagnosed as grown-ups with another psychiatric ailment—:antisocial personality disorder, a condition often accompanied by drug abuse. These volunteers likely became adult drug abusers because of this condition, not because of stimulant treatment as children, Mannuzza says.

Mannuzza's team studied 176 white, middle-class boys, ages 6 to 12, who were treated for ADHD with methylphenidate, often marketed as Ritalin. None of these youngsters displayed conduct disorder, regarded as a precursor of antisocial personality disorder.

Follow-up interviews with volunteers occurred at around ages 18 and 25. The researchers also tracked 178 psychiatrically healthy males from age 18 to 25.

Early stimulant treatment may protect kids with ADHD against conduct disorder, thus lowering later drug abuse rates, Mannuzza suggests.

Yet preliminary results from a large study of ADHD treatments, published in 2007, don't support that hypothesis, remarks psychologist James M. Swanson of the University of California, Irvine, a coauthor of the article. Over that study's first three years, early-treated children showed no decreased chance of acquiring conduct disorder, says Swanson.

The second new study, directed by psychiatrist Joseph Biederman of Massachusetts General Hospital in Boston, evaluated 112 boys with ADHD, ages 6 to 17, and then re-examined them 10 years later. Of those boys, 82 received stimulant treatment for all or part of the follow-up period.

In early adulthood, treated and untreated boys displayed comparable drug abuse rates, similar to those reported for late-treated boys by Mannuzza. But Biederman's group found no tendency for early stimulant treatment to protect against later drug abuse.

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