The favorable effect of the ACE-DD homozygous genotype on PANSS depression factor upon antipsychotic treatment, which was observed among female patients in the current study, might be explained by data previously reported by Nani et al. [4], indicating that risperidone treatment increases ACE activity, mainly among ACE-DD homozygous individuals (Table 3 and Table 4). This evidence concerns the gene ACE and major depressive disorder.