The data of COMT genotype and allele frequencies in study groups is presented in Table 1. The frequency of the COMT*L/*L genotype in controls (22%) was similar to that previously reported in European populations [5].The frequencies of alleles were nearly equal in the control group: 48% (COMT*H) and 52% (COMT*L).

Significant differences were found in the genotype frequencies between controls and subjects with schizophrenia (χ²=17.06, P=0.001, df=2), out-directed aggressive behavior (χ²=8.27, P=0.02, df=2), and self-directed aggressive behavior (χ²=12.12, P=0.004, df=2).

The significant increase of the COMT*H/*H genotype frequency was observed in the group of schizophrenic patients (χ²=17.06, P=0.0005, df=1, OR=2.56, 95%CI 1.60-4.12), both the group of subjects with out-directed aggressiveness (χ²=5.05, P=0.025, df=1, OR=1.84, 95%CI 1.08-3.16) and the group of subjects with suicidal behavior (χ²=11.19, P=0.0016, df=1, OR=2.28, 95%CI 1.39-3.77).

The frequency of the COMT*H/*L genotype seemed to be lower in schizophrenic group (χ²=7.24, P=0.009, df=1, OR=0.57, 95%CI 0.38-0.85), while the COMT*L/*L genotype had lower frequency in the group with out-directed aggressive behavior (χ²=4.29, P=0.038, df=1, OR=0.54, 95%CI 0.30-0.97).

In all investigated groups the frequency of the COMT*H allele was higher than the COMT*L allele. Significant differences were found in allele frequencies between controls and schizophrenic group (χ²=14.37, P=0.003, df=1), out-aggressive behavior group (χ²=6.70, P=0.01, df=1) and suicidal group (χ²=7.87, P=0.006, df=1).

So, according to our data the Val158/108Met polymorphism of the COMT gene is associated with schizophrenia and different forms of aggressive behavior.

Table 1. Genotype and allele frequencies of the COMT gene Val158/108Met polymorphism in investigated groups

Groups	N	p ± sp (95%CI)
		genotypes			alleles
		*H/*H	*H/*L	*L/*L	*H	*L
Control	203	0.18 ± 0.03 (0.13-0.24)	0.60 ± 0.03 (0.53-0.67)	0.22 ± 0.03 (0.17-0.29)	0.48 ± 0.02 (0.43-0.53)	0.52 ± 0.02 (0.44-0.57)
Schizophrenia	236	0.36 ± 0.03 (0.29-0.42)	0.46 ± 0.03 (0.40-0.53)	0.18 ± 0.03 (0.14-0.24)	0.59 ± 0.02 (0.54-0.63)	0.41 ± 0.02 (0.37-0.46)
Aggressive behavior    out-directed	182	0.30 ± 0.03 (0.23-0.37)	0.56 ± 0.04 (0.49-0.63)	0.14 ± 0.03 (0.10-0.20)	0.58 ± 0.03 (0.52-0.63)	0.42 ± 0.03 (0.37-0.48)
in-directed	182	0.33 ± 0.03 (0.26-0.40)	0.50 ± 0.04 (0.43-0.58)	0.17 ± 0.03 (0.12-0.23)	0.58 ± 0.03 (0.53-0.63)	0.42 ± 0.03 (0.37-0.47)

N – value, s_{p –} frequency mistake, 95%CI – confidential interval,