Allelic and genotypic comparisons within gender showed statistically significant differences only in males (Tables 2 and 3). Unlike the results obtained with the whole sample, patient and control males differed in the frequency of the A1 allele (χ2 = 5.08, df = 1, P = 0.024, odds ratio = 1.65 [95% CI 1.07–2.57]). The logistic regression analysis revealed an interaction between DRD2 alleles and gender (Table 4), such that the frequency of A1 allele was higher in patient than control males (Table 2). Similarly to the results obtained with the whole sample, patient and control males differed in genotype distribution (χ2 = 8.72, df = 2, P = 0.013). In this case, the logistic regression analysis did not reveal an interactive effect of DRD2 genotypes and sex (data not shown).
