Although the genetic correlations among the 11 disorders were somewhat consistent with the concept of a general p-factor, a hierarchical factor model that specified such a p-factor was found to offer limited biological insight, obscuring patterns of genetic correlations with external biobehavioral traits, enrichment within specific biological annotations, and associations with individual variants. Compared to the hierarchical model, a bifactor model identified a larger number of GWAS hits for p, but continued to exhibit a great deal of SNP-level heterogeneity. Given that a p-factor was found to be insufficient for accounting for patterns of multivariate associations at biobehavioral and variant levels of analysis, the question arises: what processes give rise to the moderate genetic correlations observed among the four, first-order factors? One possibility is that genetic correlations among the four factors originate from shared biology underlying pairwise combinations of factors and not from any biology that is shared across all factors. Similarly, genetic correlations among the factors themselves may reflect combinations of shared biology among subsets of disorders spanning factors that are not shared across all disorders within the corresponding factors.
