This study examined the point prevalence of TS and CT as well as rates of co-occurring OCD and ADHD in the population-based ALSPAC birth cohort. Both the TS Narrow and TS Intermediate definitions produced prevalence estimates (0.3% and 0.7%, respectively) that fall within the range of 0.3% to 0.8% reported by most population-based TS prevalence studies of school-age children over the past decade.8,10,11,17,18,20 Although some recent studies reported significantly higher TS rates (3%27 and 3.8%28), these studies were confounded by small sample size and low participation rates, respectively.7 Similarly, the only prior population-based study to report a markedly lower TS prevalence rate (0.04%) assessed subjects in late adolescence when tics often diminish or disappear.2,15 Thus, the rates observed in the current study, combined with the minimal heterogeneity observed between TS Narrow and TS Intermediate, suggest that either definition could serve as a reasonable proxy for TS in future studies.
