Using Genomic SEM, we performed multivariate genome-wide association analysis by estimating SNP associations with EXT, which is our main discovery analysis (Supplementary Information section 3.4). The estimated effective sample size of the “externalizing GWAS” is Neff = 1,492,085, and the mean χ2 and genomic inflation factor (λGC) are 3.114 and 2.337, respectively. LD Score regression suggested polygenicity rather than bias from population stratification10,12, as the (default settings) LD Score intercept and attenuation ratio were estimated to be 1.115 (SE = 0.019) and 0.054 (SE = 0.009), respectively.
