In simple terms, a polygenic risk score is a cumulative index of measured genetic liability to a disorder. PRS are similar to “heritability” (h2) in that they represent, to some degree, the aggregate and additive effects of segregating loci of small effect (see also section: Differences from other Heritability Metrics). Similar to traditional twin estimates of narrow heritability, PRS are additive in nature, consistent with numerous illustrations that support the widespread role of additivity in complex genetics (Hill et al., 2008). Several excellent reviews, both of a technical/practical and interpretive nature, have been written about the utility of PRS (Wray et al., 2014, Chatterjee et al., 2016, Bogdan et al., 2017, Plenge et al., 2013, Dudbridge, 2016). Here, we provide a brief theoretical and practical overview, before exemplifying how PRS approaches have begun to inform the field of clinical psychology and considering ways forward.
