5-HTTLPR effects on lifetime depression and BSI depression showed several similarities. Using regression analysis, there were no significant main effects of 5-HTTLPR genotypes on reported lifetime depression or on BSI depression (Table 2). However, with the increasing number of s alleles, subjects proved to be more vulnerable to the depressogenic effect of the increasing number of RLEs (Table 2 and Fig. 1A and 1C, and Table E in S1 File). These interaction effects became non-significant in the two subpopulations split by age, possibly because of decreased power, although in all cases the s allele remained the risk one (Table 2 and Figs. B-A—B-D in S1 File). The significant interaction of 5-HTTLPRxRLE was not due to the increased number of RLE in the s allele carriers. On the contrary, number of RLEs tended to decrease with the increasing number of s alleles (Table C in S1 File).
