The population-based deCODE samples were used to: 1) independently replicate the 39 top LD-independent SNPs (r2<0.2 and MAF>0.01; p<1.0×10−5) in the primary meta-analysis, followed by a sign test to examine consistency in the direction of effects in these top SNPs across the two datasets, as well as a targeted meta-analysis of these 39 SNPs using the inverse-variance method (Supplemental Methods); and 2) examine the genetic relationships between Tourette and other tic disorders through polygenic risk score (PRS) analyses (Supplemental Methods) (23). Logistic regressions were performed to test the prediction power of PRS for Tourette syndrome and tic disorders cases versus controls, adjusted by sex, year of birth, and the first 20 principal components (24).
