Although a GWAS on populations of European ancestry found no direct associations between HLA and an increased risk of depression, 14 HLA alleles (including HLA-DQB1*02, *03, HLA-DRB1*03, *07, *13, *15) have been shown to be associated with several autoimmune diseases (multiple sclerosis, Crohn’s disease, primary adrenocortical insufficiency, systemic lupus erythematosus, psoriasis vulgaris, type 1 diabetes mellitus). This evidence concerns the gene HLA-DQB1 and Crohn disease.