To explore the hypothesis that the lower heritability of the Tourette GWAS2 sample might have arisen from the inclusion of Tourette cases diagnosed in the community and ascertained using a validated web-based screen (12, 13), the GWAS2 case-control sample was divided into clinic-based cases vs. web-based cases, and the LMM-based heritability analyses were repeated. Contrary to the predicted hypothesis, both subsets had the same heritability (h2g GWAS2-clinic=0.29, SE=0.07; p=1.2×10−9; h2g GWAS2-web=0.28, SE=0.10; p=1.2×10−9) (Table 2).
