title: The prevalence of Gilles de la Tourette syndrome in children and adolescents with autism: a large scale study.
abstract: BACKGROUND
  An earlier small-scale study of children with autism revealed that 8.1% of such patients were co-morbid for Gilles de la Tourette syndrome (GTS). The present study is a large scale test of whether this result replicates.
  
  
  METHODS
  Four hundred and forty-seven pupils from nine schools for children and adolescents with autism were screened for the presence of motor and vocal tics.
  
  
  RESULTS
  Subsequent family interviews confirmed the co-morbid diagnosis of definite GTS in 19 children, giving a prevalence rate of 4.3%. A further 10 children were diagnosed with probable GTS (2.2%).
  
  
  CONCLUSIONS
  These results indicate that the rate of GTS in autism exceeds that expected by chance, and the combined rate (6.5%) is similar to the rates found in the smaller-scale study. Methodological considerations and alternative explanations for an increased prevalence are discussed.
authors.affiliation: Department of Experimental Psychology and Psychiatry, University of Cambridge.
authors.forename: S
authors.initials: S
authors.lastname: Baron-Cohen
authors.forename: V L
authors.initials: VL
authors.lastname: Scahill
authors.forename: J
authors.initials: J
authors.lastname: Izaguirre
authors.forename: H
authors.initials: H
authors.lastname: Hornsey
authors.forename: M M
authors.initials: MM
authors.lastname: Robertson
mesh_terms: D000293:Adolescent; D000328:Adult; D001321:Autistic Disorder / Q000150:complications* / Q000523:psychology; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D005879:Tourette Syndrome / Q000453:epidemiology*