Gillespie NA, Bates TC, Hickie IB, et al. - Researchers analyzed a total of 2,007 young adult Australian twins (66% female) to determine the heritability of non-medical use of over-the-counter or prescribed analgesics (NMUA) and to identify sources of genetic and environmental covariance with cannabis and nicotine use, cannabis and alcohol use disorders, and nicotine dependence. They undertook biometrical genetic analyses or twin methods using structural equation univariate and multivariate modeling to perform this study. In this sample, 19.4% reported life-time NMUA. Moderate heritability for NMUA was suggested in young male and female adults in Australia and there also appeared to be a moderate correlation of NMUA with cannabis and nicotine use and nicotine dependence. They identified it to have largely distinct genetic etiology vs that of cannabis and alcohol use disorders.