Psychiatric disorders are genetically influenced complex traits, with heritability estimates ranging from 28% (generalized anxiety disorder) to 85% (bipolar disorder; Bienvenu et al., 2011). Accumulating evidence suggests that disruptions in common biological pathways may underpin multiple forms of psychopathology (Smoller, 2013). The Cross-Disorder Group of the Psychiatric Genomics Consortium (PGC1) recently identified common single nucleotide polymorphisms (SNPs) that jointly influence liability to five major mental disorders—attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (AUT), bipolar disorder (BIP), major depressive disorder (MDD), and schizophrenia (SCZ)—and thus likely represent shared genetic etiology (Cross-Disorder Group of the Psychiatric Genomics Consortium, 2013; Lee et al., 2013). A more recent study performed by the Network and Pathway Analysis Subgroup of the PGC uncovered common genetic pathways underlying SCZ, BIP, and MDD (Network and Pathway Analysis Subgroup of Psychiatric Genomics Consortium, 2015), providing additional support for a biological contribution to shared liability to major psychiatric illnesses.
