File:Predictive power of future PGSs (polygenic scores).jpg

English: Predictive power of future PGSs (polygenic_scores). Currently attainable predictive power of PGSs (“Largest GWAS”) and projected explanatory power of future PGSs derived from discovery samples of 1M and 2M individuals (“~1M” and “~2M”). For each trait, we calculate h²_SNP directly from Eq. 3. We assume M = 70,000, and using values of R 2 and N from the largest published GWAS of the trait (e.g., 6.9% and 405,000 for education). Implied SNP-based heritabilities are 15, 16 and 30%, respectively. Parameterizations based on estimates of SNP-based heritabilities (25, 25 and 50%) yield higher projections.

To be clear, for all three traits, a substantial gulf remains between the predictive power of the PGSs and the estimates of twin and family studies. The currently attainable degree of predictive power is roughly 15–20% of the behavior–genetic estimates implied by the correlations in the figure. One important source of the gap is that the estimand in behavior–genetic studies is the proportion of variance explained by all genetic factors, including those not captured (“tagged”) by standard genotyping arrays currently used in GWASs. PGSs constructed from common variants therefore have a lower theoretical upper bound than the twin and family estimates. This bound, known as the SNP heritability, can be estimated given suitable SNP data. Published estimates suggest common variants account for about 50% of variation in human height, and around 25% of variation in traits such as BMI and educational attainment.