From petty crime to violent aggression, the likelihood of re-offending went down, according to a study from Karolinska Institutet that followed 25,000 people over a four-year period.
"It's said that roughly 30 to 40 percent of long-serving criminals have ADHD. If their chances of recidivism can be reduced by 30 percent, it would clearly affect total crime numbers in many societies," study co-author Paul Lichtenstein said in a statement.
Supervisors at several prisons that participated in the study said on Thursday that medication had vastly improved the inmates' concentration and helped them socially.
Many of ADHD researcher Ylva Ginsberg's patients felt they were not in control of their own behaviour before taking medication.
"They say that before, it was like a car driving ahead of them at 200 kilometres per hour and they were just trying to keep up," Ginsberg told Sveriges Radio on Thursday.
"Then they got the medicine and they were suddenly in the driver's seat, and driving slower."