Our finding of an imperfect genetic correlation replicates earlier results from smaller samples16,17. This imperfect genetic correlation is an important factor to consider in power calculations and study design. In the Supplementary Note, we report exploratory analyses that aim to identify specific sources of measurement heterogeneity or gene-environment interaction that may explain the imperfect genetic correlation. Unfortunately, the estimates are noisy, and the only strong finding was that SNP heritability was smaller in cohorts whose measure of EduYears is derived from questions with fewer response categories.
