People with attention deficit hyperactivity disorder (ADHD) are significantly less likely to engage in criminal behavior when they are taking medication.

The finding came from a large-scale registry study conducted at Karolinska Institutet in Sweden and was published in the New England Journal of Medicine (NEJM).

Prior studies have indicated that individuals with ADHD have a higher chance of committing a crime. However, it is unknown how receiving treatment for the disorder may impact this risk.

Over a four-period (2006-2009), the researchers analyzed more than 25,000 patients with ADHD from various registries in order to observe the association between ADHD medication and criminality.

The results showed links between ADHD medication and a lower chance of criminality in a few different ways. For example, people receiving medication had a lower incidence of criminal behavior than those not receiving treatment.

The research also demonstrated that when patients took ADHD medication, they experienced a significant reduction in their criminality risk of 32%, compared to when they did not receive any medication.

Analyzing the same individuals with and without medication was beneficial, because it demonstrated that the reduced risk was not due to any differences between subjects taking ADHD drugs and those who were not. There were no sex differences seen in the results, and the association applied equally to minor crime as it did to severe and dangerous crime.

Henrik Larsson, Associate Professor at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, explained:

“We have shown that ADHD medication very probably reduces the risk of crime. However, 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.”

Professor Paul Lichtenstein, co-author and from the same department, added: