Review articleThe international prevalence, epidemiology, and clinical phenomenology of Tourette syndrome: A cross-cultural perspective
Abstract
The overall international prevalence of Tourette syndrome (TS) is 1% in the majority of cultures of the world. Both TS and tics are certainly more obvious and may be more common in younger people. Moreover, TS is seen less frequently in some cultures. However, in all cultures where it has been reported, the phenomenology is similar, highlighting the biological underpinnings of the disorder. This article reviews the international prevalence, epidemiology, and clinical phenomenology of TS, from a cross-cultural perspective.
Introduction
The generally accepted international diagnostic criteria for Tourette syndrome (TS), a childhood onset neuropsychiatric disorder, include multiple motor tics and one or more phonic (vocal) tics or noises, lasting longer than a year [1], [2]. The age at onset of TS ranges from 2 to 21 years, with a mean of 7 years being most commonly reported. The tics are at their most severe at around 10–12 years and then reduce in severity in the majority of cases by the age of 18 years; therefore, it has been pointed out that the 1-year diagnostic criterion can cause unnecessary anxiety for some children whose TS becomes quite mild after the first year or so [3]. The onset of the phonic tics is usually later, many studies reporting it at around 11 years. Other important but less common symptoms include copying behaviors (echo phenomena), repeating one-self (pali phenomena), swearing involuntarily and inappropriately as a tic (coprolalia), and self-injurious behaviors (SIBs) [4], [5], [6], [7].
The prevalence and epidemiology of TS are more complex than was once thought. Until fairly recently TS was considered to be a rare and, according to some, a psychogenically mediated disorder [8]. The prevalence of TS depends, at least in part, on the definition of TS, the type of ascertainment, and epidemiological study methods used [9], [10]. Clinicians working in dedicated specialist TS clinics have long been aware that the majority of patients have positive family histories of tics or TS; moreover, large extended multiply affected TS pedigrees also indicate that many family members have undiagnosed tics or TS [11], [12]. Following these early observations, it was first realized that TS was far from uncommon.
In two recent papers [9], [10], one of the authors (MMR) undertook the following: (i) conducted personal research, (ii) performed a thorough literature review, and (iii) obtained unpublished data from two PhD theses in another language from other sources, the results and relevant parts of which were translated into English. After a brief summary of those findings, this article puts them in a cross-cultural perspective.
Section snippets
Epidemiology of Tourette syndrome
Early epidemiological studies reported that TS was uncommon or even rare, for a variety of reasons. More recently, however, two pilot studies and 13 large definitive studies in mainstream schools and school age youngsters in the community, using similar multistage methods, and personal interviews with the individuals under investigation, have documented remarkably consistent findings, demonstrating prevalence figures for TS of between 0.4% and 3.8% for youngsters between the ages of 5 and 18
How many Tourette syndrome(s)?
Although TS is essentially a chronic tic disorder, in the majority of cases there are other associated comorbid conditions such as obsessive–compulsive disorder (OCD) and attention-deficit hyperactivity disorder (ADHD) [4], [6], [46]. The exact prevalence of TS in these individual subtypes and those individuals with or without OCD and ADHD is unknown. In addition, coprolalia is uncommon, occurring in only 10–15% of TS patients in the community and in about 30% of TS clinic patients. In a
Cross cultural issues in Tourette syndrome
TS has been reported from all over the world and from all sociocultural, socioeconomic, religious, linguistic, and ethnic groups. However, while the disorder has been researched extensively in the Western populations, the clinical characteristics and associated features are less well known in non-Western cultures. The low prevalence in some early studies may well be due to a lack of awareness of TS, or it may be a true reflection of low prevalence as in some populations TS does appear rare. The
Conclusions
In summary, the overall international prevalence of TS according to current diagnostic criteria is around 1% in the majority of cultures worldwide, where the phenomenology is similar, highlighting the biological underpinnings of the disorder. Interestingly, in Georges Gilles de la Tourette's original description [86], the symptoms of what is now known as TS included multiple motor tics, coprolalia, echolalia, and minor motor incoordination. With those criteria, much fewer individuals would be
Acknowledgments
The authors wish to thank the Tourette Syndrome Association (USA), the Tourette Syndrome Foundation of Canada, and Tourettes Action (UK) for their continuing support.
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