analyses. For the genetic factor analyses, GWAS summary statistics from the meta-analyses for each AUDIT item were subjected to standard quality control practices, as described above. Genomic Structural Equation Modeling’s multivariable version of LD score regression was then used to estimate the genetic covariance and sampling covariance matrices (S and V, respectively) for the AUDIT items, which were used to test the specified confirmatory factor models. The S matrix was smoothed beforehand as it was slightly non-positive definite. Factor extension analysis was used to estimate the expected factor loading of item 6 (i.e., ‘eye opener’; Supplementary Material 5.1.1), as it was excluded from the final genetic confirmatory factor model due to non-significant SNP heritability.
