Prevalence of tic disorders and Tourette syndrome in a Swedish school population.

The aim of the study was to find the epidemiological distribution of tic disorders and Tourette syndrome (TS) in Swedish school children aged 7 to 15 years. A total population of 4,479 children and their parents were asked to fill in a questionnaire covering both motor and vocal tics. A three-stage procedure was used: screening, interview, and clinical investigation. Two hundred and ninety-seven children (190 males, 107 females) were found to have tics. TS, according to DSM-IV criteria, was found in 0.6% of the total population, another 0.8% had chronic motor tics, and 0.5% had chronic vocal tics. Further, 4.8% of the children had transient tics. All together 6.6% of 7- to 15-year-old children currently had or had experienced some kind tic disorder during the last year. Prevalence of different tic disorders was higher among younger children and in males, and was highly associated with school dysfunction. The prevalence of TS was higher than was previously thought but other tic disorders were more common in this childhood population.