Background: Suicidal behaviour is the leading cause of mortality from external causes at all ages worldwide. More than a million people commit completed suicide each year. According to the World Health Organisation, 25-50% of suicide victims suffered from alcohol and other substance use disorders, 22% of all suicide deaths were attributable to alcohol use (WHO, 2014). Several papers have suggested potential associations of insomnia and increased suicide risk in patients with alcoholism. We hypothesise that mutations in melatonin receptor genes may be associated with suicide risk in patients with alcoholism.

Methods. The Insomnia Severity Index (ISI) was used as a tool to assess the presence and severity of insomnia. The Columbia Suicide Severity Rating Scale (C-SSRS) was used as a method to examine suicidal behavior. Genotyping of MTNR1A (rs34532313), MTNR1B (rs10830963) genes was performed using real-time polymerase chain reaction (RT-PCR). A comparative genetic study of two groups of patients was carried out: the first group, patients with alcohol dependence syndrome (F10.2); the second group, patients with alcohol dependence syndrome (F10.2) and insomnia, which persisted 7-14 days after starting alcohol withdrawal therapy.

Results. Suicidal thoughts and a history of auto-aggressive behaviour were more common in subjects with insomnia in the post-withdrawal period. Carriers of the TT genotype of the MTNR1A gene (rs34532313) were more likely to have suicidal thoughts and a history of suicide attempts in a genetic study of patients with insomnia.

Conclusions. Our study found that the TT genotype of the MTNR1A gene (rs34532313) is a genetic marker of suicidal behaviour risk in patients with insomnia in the post-withdrawal period. However, the same pattern was not observed in patients without insomnia.