in substance use behaviors, suggesting that the same genes responsible for conferring risk for alcohol use problems may be simultaneously influencing environmental exposure as well. One safeguard against confounds driven by multiple social influences involved in GxE and gene-environment correlations are studies of experimentally manipulated environmental exposures, such as those involving randomized clinical trials or lab experiments (Manuck and McCaffery, 2014), but these studies have only recently emerged (see van Ijzendoor et al., 2011 for an example).
