The PGC has two major goals. Aim 1 is to conduct five separate GWAS mega-analyses for ADHD, autism, bipolar disorder, major depressive disorder, and schizophrenia. The Aim 2 cross-disorder mega-analyses have two components. The “nosological” sub-aim takes cases as defined by DSM-IV criteria and looks for SNPs that are compellingly associated with two or more disorders and effectively searches for genomic regions with pleomorphic effects. The “heterogeneity” sub-aim reclassifies subjects according to pre-specified phenotypic characteristics (e.g., subjects with bipolar disorder with two manic and dozens of depressive episodes should be more major depression-like than bipolar-like). This is a convenient segue to the next crucial issue – are psychiatric phenotypes qualitatively different from other biomedical diseases?
