Two-single nucleotide polymorphisms (SNPs) haplotype in the IL-33 gene, specifically rs11792633 and rs7044343, moderated the link between women’s history of childhood abuse and their history of recurrent MDD (rMDD), such that the link between childhood abuse and rMDD was stronger among women with fewer copies of the protective IL-33 CT haplotype. Here, IL33 is linked to major depressive disorder.