Impairments in cognitive functions in alcohol and other substance use disorders have been reported, but this association is not well known in population-based or genetically informative samples.

Substance use disorders and cognitive abilities are influenced by genetic factors, but the degree to which their genetic background overlaps is unknown. Substance use problems often co-occur with low education, but the genetic and environmental background of this cooccurrence is also poorly understood. This study examined cognitive functioning and other correlates of substance use disorders in two population-based samples of young Finnish adults, one of which consisted of mono- and dizygotic twin pairs enabling genetically informative analyses. Alcohol use disorders were common among young adults, and they were inversely associated with verbal cognitive ability and educational level in both samples. Biometrical analyses of the twin data suggested that alcohol dependence, verbal ability and educational level were moderately heritable, and that they were influenced by partly shared genetic factors. Educational level also moderated the importance of genetic influences on alcohol problems.