found evidence only for common genetic influences on cannabis, cocaine, hallucinogen, sedative, stimulant, and opiate dependence (Kendler, Jacobson, et al., 2003): individual genetic paths to risk for abuse of each drug separately were not strong in this study. Collectively these findings highlight the importance of shared genetic mechanisms among a range of externalizing and substance pathology but also to a potentially important role for unique genetic and nongenetic factors on specific types of substance dependence including alcohol dependence.
