Using a combined coding of presence of risk alleles (no risk group = 5-HTTLPR LL and one or two copies of CRHR1 TCA; CRHR1 risk only = 5-HTTLPR LL and 0 copies CRHR1 TCA; 5-HTTLPR risk only = 5-HTTLPR SS or SL and one or two copies CRHR1 TCA; and combined risk group = 5-HTTLPR SS or SL and 0 copies CRHR1 TCA), lower levels of child abuse severity are sufficient to elicit clinically relevant symptoms of depression in individuals with both genetic risk factors, as compared to the no risk or single genetic risk groups (see Fig. 3B). Here, CRHR1 is linked to depressive disorder.