SNP acted through the externalizing factor, we estimated QSNP heterogeneity statistics genome-wide with Genomic SEM (Supplementary Information section 3.5.1). The null hypothesis of the QSNP test is that SNP effects on the constituent phenotypes operate (i.e., are statistically mediated) via the EXT factor, so a significant QSNP test indicates that the SNP effects are better explained by pathways independent of EXT. The QSNP analysis identified substantial heterogeneity (160 near-independent genome-wide significant QSNP loci), but reassuringly, did not identify heterogeneity among 99% (571/579) of the EXT SNPs (Supplementary Table 10). An analysis of sign concordance further supported homogeneity among the EXT SNPs (Supplementary Information section 3.5.4).
