Polygenic score analyses were conducted to test two related hypotheses: 1) that both TS and OCD individually harbor multiple, small effect, common risk alleles across the genome; 2) that TS and OCD may have shared common risk alleles (cross-disorder analyses). In the individual disorder analyses, risk scores derived from the “OCD - TS/CT” discovery sample strongly predicted case-control status in the OCD target sample (p=2.1×10−4), explaining 3.2% of the phenotypic variance (Figure 3, Table S3). In contrast, risk scores derived from the TS discovery sample demonstrated only weak prediction in the TS target sample (p=0.06; R2=0.6% variance explained). Risk scores derived from the combined TS/OCD discovery sample also predicted case-control status in the OCD target sample (p=0.0075, R2=1.7%), though less robustly than those derived from the OCD discovery sample alone (p=0.01, Figure 3, inset). Risk scores derived from the TS/OCD combined sample could not discriminate between cases and controls in the TS target sample (p=0.4, Figure 3, Table S3).
