STOCKHOLM: Medication can reduce the number of crimes committed by people suffering from attention deficit hyperactivity disorder (ADHD) by one third, according to a Swedish study released on Thursday.

When comparing the behaviour of adults suffering from the disorder during periods when they were medicated, with periods when they weren't, researchers found that medical treatment reduced the risk of committing crimes by 32 per cent.

Individuals with ADHD have previously been shown to be at greater risk of entering a life of crime.

“It's said that roughly 30 to 40 per cent of long-serving criminals have ADHD,” said Paul Lichtenstein, co-author of the study at the Karolinska Institute in Stockholm.

“If their chances of recidivism can be reduced by 30 per cent, it would clearly affect total crime numbers in many societies.”

The study, which tracked more than 25,000 people over four years, found that medication had the same effect on those who had committed relatively minor infringements, as on those involved in more serious and violent crimes.

All of the participants were adults, and there was no difference in the outcome for men and women.

Five per cent of school children and around half has many of all adults have ADHD, according to the Karolinska Institute. Symptoms of the disorder, which include poor concentration, hyperactivity and impulsive behaviour, can be treated with central stimulants.

However, concern has been raised over a steep rise in medical prescriptions for ADHD in recent years, and some medical professionals have claimed alternative treatments such as psychotherapy and less potent drugs may be better suited for some patients.

“We need to point out that most medical treatments can have adverse side effects, so risks must be weighed up against benefits and the individual patient's entire life situation taken into consideration before medications are prescribed,” said Henrik Larsson, another co-author of the Stockholm study.