The prevalence of Gilles de la Tourette syndrome in children and adolescents with autism: a large scale study
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.
Method. 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.
c1 Address for correspondence: Dr Simon Baron-Cohen, Departments of Experimental Psychology and Psychiatry, University of Cambridge, Downing Street, Cambridge CB2 3EB.