Schizophrenia (SZ), bipolar disorder (BP), major depression (MDD) and autism spectrum disorder (ASD) are serious mental illnesses (SMIs) that affect a significant proportion of the worldwide population. Large genome-wide association studies have pointed to overlapping genetics including both common and rare variants as cause of these SMIs. A recent study published on June 16, 2026, in Genomic Psychiatry has shed some light regarding the etiology of SMIs.