These findings are in line with previously observed biological differences, such as lower plasma oxytocin levels in GG homozygotes [13] and the results reported by Costa et al. [32] in an Italian sample, which showed a positive association between the GG genotype of OXTR_rs53576, OXTR_rs2254298, and unipolar depression [5]. The gene discussed is OXTR; the disease is major depressive disorder.