Interleukin (IL)-8 polymorphisms contribute in suicide behavior

Previous studies have highlighted the role of immune dysregulation in suicide behavior. Interleukin (IL)-8 is a chemokine with neuroprotective effects whose lower serum concentrations have been detected in individuals committed suicide. In the present study, we genotyped three single nucleotide polymorphisms (SNPs) within IL-8 gene (rs4073, rs2227306 and rs1126647) in 229 individuals who attempted suicide with soft suicide methods, 235 suicide victims and 290 individuals without any history of psychiatric disorders or suicide attempt. The T allele of rs4073 was significantly over-represented in suicide attempt group compared with both control and completed suicide groups (adjusted P values of 8.3E-7 and 9.8E-8 respectively). This SNP was associated with suicide attempt in both dominant and co-dominant models (P values of 6.2E−9 and 4.3 E−8 respectively). The genotype and allele frequencies of other SNPs were not significantly different among the three study groups. The T C A haplotype (rs4073, rs2227306 and rs1126647 respectively) were significantly less prevalent in completed suicide group compared with suicide attempt group (OR (95% CI) = 0.63 (0.46-0.86), adjusted P value = 0.03). Besides, the A T A haplotype has significant lower frequency in individuals who attempted soft suicide compared with controls (OR (95% CI) = 0.44 (0.26-0.75), adjusted P value = 0.02). However, this haplotype was significantly more prevalent in individuals attempted hard methods compared with those attempted soft methods (OR (95% CI) = 2.21 (1.26-3.87), adjusted P value = 0.04). The present study provided further evidence for the role of IL-8 in suicide behavior.