Significant associations were also detected for homozygotes and heterozygotes compared to non-carriers in the dominant model (OR = 1.37, 95% CI = 1.13–1.66, p = 0.0013, FDR = 0.005) for the rs1800955 polymorphism in the DRD4 gene; allele C was more common in the group of patients with mental disorders. Here, DRD4 is linked to psychiatric disorder.