WASHINGTON – More than 7 million Americans are estimated to have misused stimulant drugs meant to treat attention-deficit hyperactivity disorder, and substantial numbers of teenagers and young adults appear to show signs of addiction, according to a comprehensive national analysis tracking such abuse.

The statistics are striking because many young people recreationally using these drugs are seeking to boost academic and professional performance, doctors say.

Although the drugs may allow people to stay awake longer and finish work faster, scientists who published a new study concluded that about 1.6 million teenagers and young adults had misused these stimulants during a 12-month period and that 75,000 showed signs of addiction.

The study published online this month in the journal Drug and Alcohol Dependence culled data from a 2002 national survey of about 67,000 households.

The data paint a concrete and sobering picture of what many experts have worried about for years, and present ethical and medical challenges for a country where mental performance is highly valued and where the number of prescriptions for these drugs has doubled every five years, said Nora Volkow, director of the National Institute on Drug Abuse.

“We live in a highly competitive society, and you want to get the top grades and you know your colleagues are taking stimulants and you feel pressured,” she said. “Yes, you are going to study better in the middle of the night if you take one of these medications. The problem is a certain percentage of people become addicted to them, and some have toxic effects.”

Volkow said it was impossible to disentangle the skyrocketing prescriptions of drugs for attention-deficit hyperactivity disorder from the risks of diversion and abuse.

“As a child, you have multiple friends who are being treated with stimulant medications,” she said. “You get the sense that these are good.”

Studies have shown that the drugs are highly effective, especially among children, and also that they reduce the risk of substance abuse among those correctly diagnosed with the psychiatric disorder, which is characterized by inattention and unruly behavior. Untreated ADHD has also been associated with conduct and academic problems.

At the same time, there have been growing concerns that the drugs are overprescribed. A Food and Drug Administration panel earlier this month warned that the medications carried risks of rare, but serious, cardiovascular problems, and it recommended that the agency place serious “black box” warnings on the drugs, as a way to restrain spiraling prescriptions.

Lawrence Diller, a pediatrician in Walnut Creek, Calif., who prescribes the drugs but is worried about their overuse, said that the new study showed the real health concerns are with diversion and abuse, not with rare side effects. “Seventy-five thousand addicts to prescription stimulants is much more troublesome than the 100 to 200 adults who have strokes,” he said. “Houston, we have got a problem because we are just in the middle of this epidemic.”

The study found that men and women were equally likely to be misusing the drugs, but that women seemed to be at greater risk of dependence – characterized by a lack of control, physical need and growing tolerance for the drug – while men seemed to be at greater risk of abuse, in which the medication was used in dangerous situations, said lead author Larry Kroutil, who studies health behavior and education at RTI International, a nonprofit research group.