HLA Class II Alleles and Suicidal Behavior: Evidence from a Case–Control Study

Suicidality is a complex multifactorial phenomenon strongly associated with major depression and other psychiatric disorders. Building on evidence implicating the Major Histocompatibility Complex (MHC) in modulating the immune and inflammatory processes characterizing psychiatric disorders, we hypothesized that specific HLA-DQB1 and HLA-DRB1 variants may contribute to an increased genetic susceptibility to suicidal behavior. Human Leucocyte Antigen (HLA) typing by sequence-specific primers (PCR-SSP) was performed on a sample of 196 individuals, including 70 non-lethal suicide attempters, 28 cases of completed suicide, and matched controls. The *HLA-DQB1 02/06 (RR 1.60, CI95% 1.22–2.09, p = 0.03 *) and *HLA-DRB1 11/15 (RR 1.70, CI95% 1.3–2.24, p = 0.04 *) genotypes and the HLA-DRB115~DQB103 haplotype (RR 1.58, CI95% 1.22–2.04, p = 0.03 *) were found to favor suicidal behavior. Psychosocial determinants associated with an increased suicidal risk were bereavement of close relatives (linked with HLA-DQB1*02), memory dysfunction (HLA-DQB1*06), disillusionment (HLA-DRB1*07 and HLA-DRB1*15), and self-harm (HLA-DRB1*15). Our findings support the contributory role of HLA polymorphisms in shaping susceptibility to suicidal behavior.