The prevalence of Tourette syndrome in a mainstream school population (ages 13 to 14 years) in West Essex, England has been determined by parent, teacher, and pupil questionnaires, class observations to identify tics, and subject and parent face-to-face interviews, and reported from the Section of Epidemiology and General Practice, Institute of Psychiatry, Denmark Hill, London, UK. From data available on 166 pupils in one school year, 5 children had TS, based on DSM-III-R criteria. Hyperactivity was an associated disorder in 4 and ADHD was present in 1. The prevalence estimate for TS in this age group was 299 per 10,000 pupils, or 3%. In comparison, the clinical records of the West Essex child and adolescent psychiatry service revealed 18 referred cases of TS out of a population of 37,500 children, ages 4 to 16 years, or a prevalence rate of 4.8 per 10,000 (0.05%). 
COMMENT. TS among children in a community as a whole is more common and milder than that diagnosed in a health-care psychiatry service. The relative prevalence rates are 3% in a school population compared to 0.05% in a child psychiatry service in the UK. Prior studies involving school children from Monroe County, NY and a California school district found estimated TS prevalence rates of 3 per 10,000 (0.03%) and 76 per 10,000 (0.8%), respectively. (see Progress in Pediatric Neurology I, PNB Publ, 1991;pp228-9). The prevalence of TS in the UK study is four times greater than the highest US estimate in similar populations. The authors attribute the higher TS prevalence to be related to more thorough case ascertainment methods.