HLA-DQB1 and psychiatric disorder: Considering the MHC implication in modulating the immune or inflammatory processes that characterize psychiatric disorders, we hypothesized that specific alleles, genotypes and haplotypes within the HLA-DQB1 and HLA-DRB1 loci are significantly associated with suicidal behavior, the investigation of these markers leading to the identification of new correlations between HLA polymorphisms and genetic susceptibility to suicidal behavior.