SLC6A4 and major depressive disorder: There was a statistically significant difference in distribution of SLC6A4 genotypes between BP (l/l = 28.2%, s/l = 59.3%, and s/s = 12.6%) and MDD (l/l = 31.2%, s/l = 46.1%, and s/s = 22.7%) patients (p = 0.012) (Table 3).