mediated effects of genes on substance use (e.g., Laucht et al., 2007), it precluded us from examining polygenic effects. Given that complex behaviors are known to be a result of multiple genetic effects it will be important that future studies with larger samples examine potential polygenic effects such as G×G interactions or cumulative genetic risk scores on substance use. However, there is a tradeoff when examining polygenic effects; although this approach is likely to increase the amount of variance explained in substance use, there is a reduction in biological specificity.
