of bipolar disorder. This study also acted as a proof-of-principle for PRS, showing that PRS based on thousands of common variants genome-wide, including many with no effect and using effect size estimates from published GWAS, can provide a reliable indicator of genetic liability. This has motivated several other applications, including polygenic Mendelian Randomisation (Hung et al., 2014), where causality of potential intermediate phenotypes in a disease pathway can be tested (Ehret et al., 2011), use of PRS as biomarkers, and the enrolment of clinical trial participants according to risk (Hu et al., 2013).
