LD score regression17 was used to estimate genomic inflation and heritability of the intelligence phenotypes in each of the 14 cohorts using their post-quality control summary statistics, and to estimate the cross-cohort genetic correlations39. Pre-calculated LD scores from the 1000 Genomes European reference population were obtained online (see URLs). Genetic correlations were calculated on HapMap3 SNPs only. LD score regression was also used on the age subgroup meta-analyses to estimate heritability and cross-age genetic correlations.
