Dysregulations in serotonin neurotransmission can be a strong contributing factor in suicide and impulsive-aggressive personality traits. Victims of suicide form a heterogeneous group in terms of planning, lethality and number of used methods. In this study, we tested single nucleotide polymorphisms (SNPs) of the monoamine oxidase (MAO) A and B genes on the Slovenian population, which has one of the highest suicide rates in the world. Genotyping was performed on 77 victims of complex suicide, 406 victims of simple suicide and 289 controls. The differences in allele distribution were investigated with the two-tailed χ2 test. Haplotype analysis was performed on 740 subjects. Significant or tendency for significant differences in distribution was observed for all studied polymorphisms in the MAOA gene when comparing male victims of complex suicide, victims of simple suicide and controls. Minor allele frequencies in male victims of complex suicide were A 6.7% for rs3027407, C 13% for rs909525 and T 12.7% for rs1137070; in victims of simple suicide, A 36.3% for rs3027407, C 39.5% for rs909525 and T 36.4% for rs1137070; and in controls, A 25.2% for rs3027407, C 30.4% for rs909525 and T 25.8% for rs1137070. The distribution analysis of polymorphism rs1799836 in the MAOB gene and all studied polymorphisms in the MAOA gene in females failed to show any significant results. GTC haplotype (for rs3027407, rs909525, rs1137070) in MAOA polymorphisms was more frequent in victims of complex suicide compared to that in controls and victims of simple suicide. Compared to victims of complex suicide, male victims of simple suicide were more often carriers of MAOA alleles that are, according to literature, associated with higher levels of impulsivity and anger. These differences in SNP distribution could serve as an additional method of differentiating between victims of complex and victims of simple suicide. Further studies including psychological autopsies should be carried out in order to identify personality traits and behavioural differences among distinct groups of suicide victims.
Keywords: Complex suicide; Impulsivity; Monoamine oxidase; Polymorphism; Serotonin.