Genetic and environmental risk factors in the aetiology of illicit drug initiation and subsequent misuse in women

Background Subsequent to initial exposure to the use of a psychoactive subs tance, psychoactive substance use disorder (PSUD;) may or may not develop. Aims To investigate the relationship between the risk factors for initiatio n and the subsequent misuse of psychoactive substances. Method The lifetime history of illicit substance use and misuse was obtaine d by telephone interview with 1934 members of female-female twin pairs. We apply a novel model, which estimates the role of genetic and environmental risk factors that influence initiation and those specific to misuse, to thr ee classes of illicit psychoactive substances. Results The individual-specific environment and family environment influenc ed the probability of initiation, but only individual-specific environment had an impact on the probability of subsequent misuse. Genetic factors whic h influence the risk of initiation and of misuse were identified. Conclusions Aetiological factors that influence drug initiation and subsequ ent misuse are correlated but not identical. Family environment is an impor tant determinant of risk fdr drug experimentation. Two classes of genetic r isk factors act on the liability to PSUD: those that influence the probabil ity of initiation and those that influence the risk of misuse. Declaration of interest Supported by the US National Institutes of Drug Abu se and Mental Health.