One may also use GWAS data to improve our understanding of psychiatric disorders in additional ways. Common variant heritability of disorders may be understood quantitatively by genome-wide complex trait analysis.35 This method has demonstrated substantial common variant heritability for multiple disorders,15 along with surprising demonstrations of coheritability (eg, a 70% overlap in common genetic vulnerability markers between bipolar disorder and schizophrenia). Other methods now becoming useful in research, and with the potential for clinical utility, include polygenic risk scores,36 which combine the effects of multiple loci in a single estimate of risk, and pathway analyses, which combine effects of multiple loci to understand pathophysiology. Recent data suggest emerging clinical utility for polygenic risk scores.37,38
