FIGURE 2.

Improvement in the polygenic score prediction of hippocampal volume, as power in the discovery GWAS increases. PRS may be thought of as weighted‐sum scores that summarize the results of the GWAS to a given level of significance. PRS analyses were conducted using 4,000 randomly selected unrelated participants of European ancestry from the ABCD study, which was not included in the discovery meta‐analyses (Casey et al., 2018) (relatedness <.025; ancestry defined as <6 SD from the European reference centroid in a multidimensional scaling analysis). PRS were calculated using the traditional clumping and thresholding approach (‐‐clump‐r2 0.1 ‐‐clump‐kb 1,000). Weights for these polygenic scores were derived from GWAS for hippocampal volume controlling for ICV from Stein et al., 2012, Hibar et al., 2015 and Hibar et al., 2017, a GWAS of 20,112 UK Biobank participants of European Ancestry, and a meta‐analysis of the results from Hibar et al., 2015 and the UK Biobank GWAS of 20,111 individuals. Analyses included Age, Sex, ancestry corrections (components 1–4) and ICV as covariates