We observed that carriers of at least one <i>COMT</i> rs165815 C allele had lower odds for developing visual hallucinations (OR = 0.34; 95% CI = 0.16-0.72; <i>p</i> = 0.004), while carriers of at least one <i>DRD3</i> rs6280 C allele and CC homozygotes had higher odds for this adverse event (OR = 1.88; 95% CI = 1.00-3.54; <i>p</i> = 0.049 and OR = 3.31; 95% CI = 1.37-8.03; <i>p</i> = 0.008, respectively).