Inquiries to poison control centers about teenage abuse of drugs for attention deficit hyperactivity disorder (ADHD) increased by 76 percent over the last eight years, indicating a surge in rates of the abuse itself, according to a study conducted by researchers from the Cincinnati Children's Hospital Memorial Center and published in the journal Pediatrics.

"It's more bad news on an entrenched problem," said Steve Pasierb, head of The Partnership for a Drug-Free America, who was not involved in the study.

The researchers reviewed data collected by the American Association of Poison Control Centers between 1998 and 2005. They found that the number of calls by parents, emergency room doctors and others about teenagers abusing ADHD drugs increased from 330 per year in 1998 to 581 per year in 2005, far outpacing the rate of increase in calls about other forms of teenage substance abuse. The majority of teenagers involved in the calls ended up being treated in emergency rooms, and 42 percent suffered moderate or severe side effects. Four of the teenagers died.

Far more teenagers are probably experiencing side effects, the researchers noted, since most cases of abuse don't end in calls to poison control.

During the time period covered by the study, prescriptions for ADHD drugs rose 86 percent in children between the ages of 10 and 19, from roughly four million to almost eight million.

Pasierb said that many teenagers do not understand that abuse of prescription drugs can lead to potentially fatal side effects. In the case of ADHD drugs, these can include agitation, rapid heartbeat and dangerously high blood pressure.

"They say, 'It's FDA approved, how dangerous could it be?'" he said.

Research by the Partnership for a Drug-Free America suggests that 19 percent of U.S. teenagers have abused prescription drugs, or nearly one in five.