Data were drawn from the Study of Addiction: Genetics and Environment (SAGE) (Bierut et al., 2010). Analyses focused on 2596 unrelated individuals (44% male; mean age=38.58 years [standard deviation (SD)=9.80]) of European ancestry, which was confirmed using principal component analysis. All subjects were no more related than second cousins(Palmer et al., 2015a). Additional details on SAGE are available at http://www.ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?study_id=phs000092.v1.p1.
