alcohol dependence (Fehr et al., 2006). Other studies suggest that GABRA2-related alcohol dependence vulnerability is limited to individuals with comorbid dependence on illicit drugs (Agrawal et al., 2006), or that GABRA2 markers are related to polysubstance abuse, but not alcohol dependence alone (Drgon et al., 2006). In contrast, the MTFS and SIBS samples used in the present study are community-based, reflecting psychopathology at rates and levels representative of the general population. As such, measures of the quantity and frequency of alcohol use, as well as the endorsement of alcohol-related symptomatology, are low relative to clinically-derived samples, or samples selected for a family history of alcohol-related psychopathology. Further, many participants were still in adolescence at the time of assessment (minimum age 16.5), and were therefore less likely to have ever tried alcohol, and less likely to exhibit heavy alcohol use or alcohol-related symptomatology than adult participants. However, there have been instances of GABRA2 SNPs being associated with alcohol dependence in samples drawn from the general population (eg. Covault et al., 2004).
