Our study also offers the opportunity to examine the rates of overlap among TS, OCD and ADHD cases, a comparison that has not been previously reported in a population-based sample (Figure 2 and Figure S1, available online). Only 8% to 9% of ALSPAC TS cases had all three disorders (TS+OCD+ADHD) compared with 18% to 34% of clinically ascertained TS patients.29,32 Similarly, although fewer than 30% of TS clinic patients have TS without co-occurring OCD or ADHD,29,32 nearly 70% of ALSPAC TS cases did not have either of these two major co-existing conditions. These data suggest that TS individuals in the general population, compared with those seen in specialty clinics, may be more likely to have an isolated tic disorder without OCD or ADHD. This observation, if validated in future studies, would be important for community psychiatrists and pediatricians to consider when counseling patients with new diagnoses and their families. However, it is important to note that many other neuropsychiatric conditions can be associated with TS that were not examined in this study. Other population-based studies have reported high rates of
