Further, in any analysis of gene by environment interactions, gene environment correlation is important to address. Previous research has found gene environment correlation in relation to substance use (Cleveland, Wiebe, & Rowe, 2005; Fowler et al., 2007; Rutter & Silberg, 2002), which occurs when genetics affect the likelihood of experiencing particular environmental factors. This becomes an issue when the environmental variable of interest is not randomly assigned. However, because intervention status, in this case, was randomly assigned, gene environment correlation is not an issue.
