MAGI2—the gene, linked to the identified association for quantitative HADS scale-based GWAS has diverse functions, engulfing both the support of intestinal homeostasis affected in IBD and IBS on the one hand, and development and stabilization of synapses (including GABAergic ones), HPA axis, and serotonin signaling regulation through interaction with CRHR1 and HTR2A—the processes vital for MDD pathogenesis on the other hand. This evidence concerns the gene HTR2A and major depressive disorder.