The number of young American adults taking medications for attention deficit hyperactivity disorder nearly doubled from 2008 to 2012, according to a report to be released Wednesday by the nation’s largest prescription drug manager.

The drug manager, Express Scripts, which processes prescriptions for 90 million Americans, also found that almost one in 10 adolescent boys were taking medications for the disorder, usually stimulants such as Adderall or Concerta.

Some experts said the report provided the clearest evidence to date that the disorder is being diagnosed and treated with medication in children far beyond reasonable rates, and that steeply rising diagnoses among adults might portend similar problems. These drugs can temper hallmark symptoms like severe inattention and hyperactivity but also carry risks like sleep deprivation, appetite suppression and, more rarely, addiction and hallucinations.

In examining actual prescriptions filled, the report also strongly corroborated data from several government surveys that many prominent mental health experts had discredited for relying on parents’ recollections of their children’s health care.