Conclusions

The literature on TS is increasing rapidly. Fortunately, studies with larger sample sizes are becoming more common. Several simple but important questions remain to be answered in TS, including the following: Why do tics tend to start at ages 5-10? Why are they more common in boys? Why do they tend to improve during sleep? Why do tics usually improve in early adulthood? How accurately can we predict outcome for an individual patient? Which patients need which treatments? Is secondary prevention possible? Hopefully future studies will address these and other important issues.

Competing interests

KJB participated in clinical trials supported by Neurocrine Biosciences and Acadia Pharmaceuticals.

Grant information

This work was supported in part by the U.S. National Institutes of Health (NIH), grant R01 MH104030. The authors confirm that the funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.