TS is reported worldwide.[12]Tanner C. Epidemiology. In: Kurlan R, ed. Handbook of Tourette's syndrome and associated tic and behavioral disorders. New York, NY: Marcel Dekker; 2004:399-410.[13]Comings DE, Comings BG. Tourette syndrome: clinical and psychological aspects of 250 cases. Am J Hum Genet. 1985;37:435-450.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1684588/pdf/ajhg00158-0003.pdf
http://www.ncbi.nlm.nih.gov/pubmed/3859204?tool=bestpractice.com
It affects boys more frequently than girls, at a ratio of between 3:1 and 5:1.[14]Tanner CM, Goldman SM. Epidemiology of Tourette syndrome. Neurol Clin. 1997;15:395-402.
http://www.ncbi.nlm.nih.gov/pubmed/9115469?tool=bestpractice.com
[15]Centers for Disease Control and Prevention. Data & Statistics on Tourette Syndrome. June 2021 [internet publication].
https://www.cdc.gov/ncbddd/tourette/data.html
Studies estimate its prevalence to range from 0.3% to 0.9%.[16]Scharf JM, Miller LL, Gauvin CA, et al. Population prevalence of Tourette syndrome: a systematic review and meta-analysis. Mov Disord. 2015;30:221-228.
http://www.ncbi.nlm.nih.gov/pubmed/25487709?tool=bestpractice.com
The reported prevalence is widely variable as a result of non-uniform methodologies and diagnostic criteria, such as differences in diagnostic procedures, presence or absence of psychiatric comorbidity, and sample differences. In the US, TS is estimated to have a prevalence of 0.6% in children and adolescents aged 6 to 17 years, with about half of cases undiagnosed.[15]Centers for Disease Control and Prevention. Data & Statistics on Tourette Syndrome. June 2021 [internet publication].
https://www.cdc.gov/ncbddd/tourette/data.html
In the UK, TS affects 1 per 100 schoolchildren, with most having only mild symptoms. Around 300,000 children and adults in the UK have the condition.[17]Tourette's Action (UK). What is Tourette syndrome? 2013. http://www.tourettes-action.org.uk/ (last accessed 25 July 2016).
http://www.tourettes-action.org.uk/67-what-is-ts.html?17
A majority of patients have behavioural and psychiatric comorbid symptoms or disorders; only 12% across all ages are reported to have only tics without other associated conditions.[7]Freeman RD, Fast DK, Burd L, et al. An international perspective on Tourette syndrome: selected findings from 3,500 individuals in 22 countries. Dev Med Child Neurol. 2000 Jul;42(7):436-47.
http://www.ncbi.nlm.nih.gov/pubmed/10972415?tool=bestpractice.com
From a worldwide dataset, ADHD is the most common comorbid psychiatric disorder, and accounts for about 55% of the behavioural findings.[18]Freeman RD; Tourette Syndrome International DatabaseConsortium. Tic disorders and ADHD: answers from a world-wide clinical dataset on Tourette syndrome. Eur Child Adolesc Psychiatry. 2007;16(suppl 1):15S-23S.
http://www.ncbi.nlm.nih.gov/pubmed/17665279?tool=bestpractice.com