Calls to U.S. poison control centres regarding teenagers overdosing on attention deficit medications rose 76 per cent over seven years, American researchers say in a new study.

"Calls related to teenaged victims of prescription ADHD medication abuse rose 76 per cent, which is faster than calls for victims of substance abuse generally and teen substance abuse," researchers from Cincinnati Children's Hospital Medical Center conclude in Monday's issue of the journal Pediatrics.

"The sharp increase, out of proportion to other poison centre calls, suggests a rising problem with teen ADHD stimulant medication abuse."

Callers included emergency room doctors and worried parents looking for advice on the problem of intentional misuse of the prescription drugs used to treat attention deficit hyperactivity disorder. The medications include Ritalin, known generically as methylphenidate, and Adderall, a mix of several amphetamines.

The researchers analyzed data from the American Association of Poison Control Centers for all cases of ADHD drug misuse among 13- to 19-year-olds from 1998 to 2005. Over that time, countrywide calls increased from 330 to 581 yearly.

Serious side-effects for abusers

The cases included four deaths. Overall, 42 per cent of the teens had moderate to severe side-effects, and most ended up getting emergency treatment.

The true number of teen abusers who suffered serious side-effects is likely much higher, because many cases don't result in calls to poison control centres, said study author Dr. Randall Bond, medical director of the Cincinnati hospital's drug and poison information centre.

Abuse often involves crushing and snorting the pills to speed up the effects and create a buzz, but dangerous side-effects go with it, said Mark Stein, a psychiatry professor and ADHD expert at the University of Illinois at Chicago.

When serious side-effects develop, children should be taken to the ER for treatment with sedatives, he said.

Canadian drug counsellors and researchers have also reported Ritalin abuse is a growing problem, with students selling or trading the pills. The stimulants have been abused to suppress appetite, increase wakefulness and increase focus and attention, according to the U.S. National Institute on Drug Abuse.

Bond and his colleagues did not have information on whether the abusers were teens with ADHD, but anecdotal evidence suggests many were not.

ADHD affects between five per cent and 12 per cent of children and four per cent of adults worldwide.

The findings should not deter teens with ADHD who need the drugs from using them, Stein said, given they may be at risk for abusing illicit drugs if they don't get the medications.

With files from The Associated Press