A third source of complexity arises from studies hypothesizing that demographic characteristics (e.g., sex, race and ethnicity) are likely to moderate this GxE interaction [12, 30]. Under stressful circumstances, susceptibility to depression among individuals carrying the S allele was significant only for women in several studies [11, 12, 30]. Three other studies reported no sex difference in the GxE interaction [16, 18, 24]. Although the distribution of 5-HTTLPR genotype varies substantially across racial and ethnic groups [3, 4, 7, 16, 30–32], we know of only two studies that explicitly tested an interaction among race, stressors, and 5-HTTLPR in a model of depression. These studies found no difference in the GxE interaction between blacks and whites [30] or between Asians and non-Asians [16].
