In the first major study of the use of medications for attention deficit hyperactivity disorder (ADHD), researchers found that parents of children on ADHD drugs were nine times more likely than other parents to use the drugs as well. As well, they found that if at least one parent and child were taking an ADHD medication, a second child was more likely to do so, too.

Physicians have long understood that ADHD runs in families and the findings of this new study support what they see in their practices, but not without some surprising discoveries.

In families where a parent and child both began taking ADHD medications last year, nearly half the time the parent did so first, according to the study. According to Dr. Thomas E. Brown, associate director of the Yale Clinic for Attention and Related Disorders, “Usually it’s the kid first, then the parent.”

In households where a parent and child first began taking the drugs last year, nearly 60% of the time it was the mother rather than the father, though ADHD is 2 to 3 times more common in men than women.

Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at Schneider Children’s Hospital in New Hyde Park, NY, explained that more women are being examined for attention deficit problems.

The study, by prescription benefit manager Medco Health Solutions, was based on analysis of prescription claims filed in 2005 for more than 107,000 children aged 5-19 and their parents.

Among children taking ADHD medications, 7% had a parent also on the medicine. Among twins with one taking an ADHD drug, there was a 25% chance the other was also on the drug – 33% if both twins were male.

Brown explained, “When people have the opportunity to see how much these medications improve a person’s function and they see it every day in their own family, they’re more likely to consider using these medicines.” He also said people would be less deterred by heavily publicized side effects.

Continuing, Brown said that the drugs are safe for most people and that the risks of alcohol and drug abuse, plus work and family issues, are much higher for those that don’t receive adhd treatment.

The average age for patients to begin ADHD drug therapy was 43 for adults and 13 for children. Experts say attention problems become most obvious when kids hit middle and high school.

According to Medco, between 2000 and 2004 ADHD drug-use rose about twice as fast among adults as children and climbed at a much higher rate among women than men.