The prevalence of Tourette syndrome in a mainstream school population

Abstract

The aim of this study was to ascertain accurately the prevalence of Tourette syndrome (TS) in a mainstream school population. All year 9 pupils (aged 13 to 14 years) in a mainstream secondary school were investigated using a twostage procedure. Standardized questionnaires were completed by parents, teachers, and pupils. CIass observations were also carried out to identify tics. Those pupils identified as having tics underwent a semistructured interview to determine whether they had TS according to DSM-III-R criteria. Data were available from'at least one source (parent, teacher, or self-reports) on 166 of the 167 pupils in the year. Five subjects were identified as having TS according to DSM-III-R criteria, yielding a prevalence estimate of 299 per 10 000 pupils in this age group. The results of this study suggest that TS in the community as a whole is more common and milder than those prevalence estimates and descriptions of the disorder based on TS encountered in secondary or tertiary health-care service settings. 1989, 1994, 1995).Most TS research has focused on describing the syndrome, its association with other psychopathologies, and o n attempting to investigate aetiological factors (Kobertson 1989, 1994). However, the populations studied have almost invariably been drawn from highly selected specialized tertiary refernl centres. Data derived from such studies will only be free from selection and attribution bhs if they are representative o f all cases of TS. This is unlikely for three main rcasons: first, complex and variable clinical filters exist, benvcen the individual with '15 in the community and specialist care, which need to be negotiated in order to access tcrtiary care; second, recognition and diagnosis ofTS is subject to variability; and third, referral may be dictated by associated bchavioural disturbance n t h e r than by 'IS itxlfwhich, in community samples. is often a mild disorder (Kurlan et id. 1986(Kurlan et id. . 1987 Kobertson and Gourdie 1990; McMahon et al. 1992).Thus, most study populations have been subject to substantial (and often unquantifiable) selection procedures which may limit the extent t o which descriptive and comorbidity data can be generalized. It is also likely that such methodologies will lead t o underestimates of the population prevalence o f the syndromc'. Prevalence estimates depcntl on accuntc data regarding the numerator (the number with thc disorder) and denominator (the size of the population from which the caws are dnwn). If the number of people identitied ;IS having ' I 3 by the rescarch methodology is only a fraction of the true number with ' l 3 then the population prevalence rate will be underestimated. In response to these difficulties, four studies have attempted to estimate the prevalence rate of -IS

VISIT-TS: A multimedia tool for population studies on tic disorders

“…The most detailed data on the sensitivity of questionnaires for tic diagnosis come from the study of Mason et al (1998). They gave questionnaires containing the 4 tic screening questions of Apter et al (1993) to students, parents and teachers.…”

“…We first reviewed previous methods including the Yale Child Study Center questionnaire ( Findley et al , 1999; Jagger et al , 1982), the Kiddie SADS semi-structured interview (K-SADS-PL) ( Kaufman et al , 1997) and the interviews used by Apter et al (1993); Gillberg & Rasmussen (1982, Appendix); Hornsey et al (2001) and Mason et al (1998) who used the Apter questions and the National Hospital Interview Schedule for GTS ( Rickards & Robertson, 2003; Robertson & Eapen, 1996); Appendix I in Khalifa & von Knorring (2003); and Table 1 in Linazasoro et al (2006). We also reviewed the Diagnostic Confidence Index ( Robertson et al , 1999), the YGTSS ( Leckman et al , 1989; Storch et al , 2005), and the parent and child self-report forms used by the Tourette Syndrome Association International Consortium for Genetics (1999).…”

“…Supporting the potential importance of this concern, epidemiological studies that included expert examination ( Comings et al , 1990; Cubo et al , 2011; Hornsey et al , 2001; Jin et al , 2005; Khalifa & von Knorring, 2003; Khalifa & von Knorring, 2005; Kurlan et al , 1994; Lanzi et al , 2004; Mason et al , 1998; Wang & Kuo, 2003) generally report a several-fold higher prevalence of tic disorders than do other epidemiological studies ( CDC, 2009; Scahill et al , 2014). …”

Tic prevalence by direct observation in an elementary school

“…Eight of the children who had no tics according to any of these reporters were then seen for 20 minutes by an expert tic clinician, who observed tics in three of the eight. 23 In fact, several studies found that direct examination identified tics unnoticed by children, parents, or teachers (and sometimes did not observe tics they had reported). In one study, κ for parent and teacher concordance was 0.30 (calculated from their data).…”