title: Review of prevalence studies of tic disorders: methodological caveats.
abstract: BACKGROUND
  Tic disorders are neurodevelopmental disorders of childhood associated with psychiatric comorbidity and academic problems. Estimating the prevalence and understanding the epidemiology of tic disorders is more complex than was once thought. Until fairly recently, tic disorders were thought to be rare, but today tics are believed to be the most common movement disorder, with 0.2-46.3% of schoolchildren experiencing tics during their lifetime. Tentative explanations for differing prevalence estimates include the multidimensional nature of tics with a varied and heterogeneous presentation, and the use of different epidemiological methods and study designs.
  
  
  METHODS
  Literature review and analysis of methodological issues pertinent to epidemiological studies of tic disorders.
  
  
  RESULTS
  Epidemiological studies of tic disorders were reviewed, and the main elements of epidemiological studies, including sample selection, case ascertainment strategy, definition of tic disorders, and the degree of coverage of the eligible population (i.e., the response rate) were examined.
  
  
  CONCLUSIONS
  In order to improve the quality of epidemiological studies of tic disorders, a number of recommendations were made, including but not limited to a review of the diagnostic criteria for tic disorders, and inclusion of new tic disorder categories for those with tics of secondary etiology.
authors: Neurology Department, Complejo Asistencial Universitario de Burgos, Spain.
authors: Esther
authors: E
authors: Cubo
keywords: Epidemiology; movement disorders; prevalence studies; screening in epidemiology; tics