We used the StructLMM approach to analyze whether DSM-IV criterion counts of AD, CaD, CoD, OD, and ND and the co-occurrence of multiple DSM-IV SD diagnoses interact at the same loci with respect to SI. We limited the genetic analysis to SI, because of the relatively low prevalence of the other suicidality outcomes in the Yale-Penn cohort (Table 1). From the StructLMM framework, we obtained evidence of: (i) loci with significant SD-related interaction effects and (ii) genetic association accounting for the possibility of heterogeneous effect sizes due to multivariate SD–gene interactions. P values were used to verify the statistical significance of the association and interaction tests in each locus. Once we identified the loci surviving multiple-testing correction, StructLMM permitted us to calculate Bayes factors (BF) to interpret evidence for environment relevance, including potential for positive and negative BFs supporting the alternate vs. null models, respectively. Specifically, the BFs were calculated between the full model and models with environmental variables removed to identify which SD-related traits are most relevant for the gene interactions observed. Additionally, we also estimated the fraction of
