Subjects. The control group consisted of 272 healthy volunteers. The age range was 15-76, with a mean ± SD of 36.7 ± 12.4 years. As significant ethnic variations in ge­netic frequencies might exist, unrelated subjects from the Russian population which belongs to a Slavic group of the Indo-European language family, and the Tatar population which belongs to a Turkic group of the Altaic language family, were randomly selected from the general popula­tion of the Volga-Urals region of Russia. All control sub­jects and their first-degree relatives have no lifetime his­tory of any psychiatric disorders or suicidal behavior. Written informed consent was obtained from all subjects after a detailed and extensive description of the study.

The attempted suicide group consisted of 188 patients of the Clinical Republic Hospital, Ufa City, Russia. The age range was 15-86, with a mean ± SD of 31.8 ± 14.8 years. Patients of Russian and Tatar descent were enrolled in the study. Systematic information on suicide attempts was collected by repeated interviews with the patients. Subjects attempted suicide with the following methods: drug overdose (81%), cutting (8.5%), jumping from a high place or under a vehicle (6.3%), hanging (4.2%).

Genotyping. Genomic DNA was extracted from pe­ripheral blood leukocytes using a standard phenol-chloro­form method. Both polymorphisms were genotyped using amplification by polymerase chain reaction (PCR) and subsequent enzyme digestion. Polymerase chain reaction was carried out in a total volume of 12.5 mL containing 100 ng of genomic DNA; 0.25 mM of the specific primers; 0.25 mM dNTPs; 0.5 units of Taq DNA polymerase (Silex, Moscow, Russia) and 1.25 mL of 10 x buffer (67 mM Tris-HCl, pH 8.8, 6.7 mM MgCl₂, 16.6 mM (NH₄)₂ SO₄, 0.01% Tween-20).

The primer pair (forward: 5’-AAG CTG CAA GGT AGC AAC AGC-3’; reverse: 5’-AAC CAA CTT ATT TCC TAC CAC-3’) was used for amplification of a 486 bp DNA fragment of the HTR2A gene. The PCR conditions for A1438G genotyping consisted of an initial 4 min. denaturation at 95°C, followed by 30 cycles of a 1 min. denaturation at 95°C, 30 seconds annealing at 60°C, 30 seconds extension at 72°C and ending with a final 10 min. extension at 72°C. The PCR products were digested with MspI for 12 hours, then electrophoresed on a 7% acrylamide gel. The G allele cleaved into 244 and 224 bp fragments, whereas the A allele was not digested [21].

The G861C polymorphism of the HTR1B gene was determined by the method of Lappalainen et al. [17]. For amplification of the 548 bp DNA fragment we used two primers (forward: 5’-GAA ACA GAC GCC CAA CAG GAC-3’; reverse: 5’-CCA GAA ACC GCG AAA GAA GAT-3’). The PCR conditions consisted of an initial 5 min. denaturation at 94°C, followed by 30 cycles of 20 seconds denaturation at 94°C, 1 min. annealing at 58°C, 30 seconds extension at 72°C, and ending with a final 5 min. extension at 72°C. The PCR products were digested with HincII for 12 hours, and then electrophoresed on a 7% acrylamide gel. The presence of the G allele yielded two fragments of 452 and 96 bp, while the presence of the C allele yielded three fragments of 142, 310 and 96 bp.

Statistical Methods. The genotype and allele fre­quency distribution of these polymorphisms were com­pared between suicidal and control groups and their sub­groups using a chi-square test with Yets’s correction; p <0.05 was considered statistically significant. Odds ratios (OR) with 95% confident intervals (CI) were calculated [22].