When men and women experience shared environments differently (Bird and Rieker 2008), whether due to biological or social factors, gender is likely to moderate the influence of genetics and/or environments in etiological pathways, leading to GxExE effects. A GxExE effect is one in which gene–environment interactions are observable in only one gender group or the magnitude or pattern of gene–environment interaction (e.g., direction) differs between the two genders (Shanahan et al. 2008). For example, because women’s drinking behavior is subjected to greater external social control by gender norms, having friends who engage in alcohol misuse might have a stronger adverse effect in men compared to women (an ExE effect). Hypothetically, then, exposure to deviant peer groups might trigger a candidate gene associated with alcohol dependence (a GxE effect), but only for men (a GxExE effect).
