Men who are on methadone treatment are twice as likely as the general population to be involved in motor vehicle accidents, according to a new study from Norway.

The researchers examined medical records of about 2,500 people who were prescribed methadone for drug addiction treatment, and found 26 were involved in motor vehicle accidents, a rate at least twice as high as that found in the general population, Reuters reports.

It is not known whether those involved in accidents were also using other drugs or alcohol, the article notes. The researchers also did not know how long study participants had been using methadone when the accidents occurred. Women in the study did not have an increased risk of car accidents.

The study appears in the journal Addiction.