Autism is a chronic and severe neuropsychiatric disorder with an early onset, characterised by qualitative impairments of social interaction, deviant development of language and other communicative skills, delayed cognitive development, and restricted repetitive and stereotyped interests and behaviours.1,2 The prevalence in the general population was estimated at 5.5/10 000 but more recent investigations report higher rates.3 Males are affected more often than females, with a predominance of 3 to 1.4 Mental retardation is present in about 75 to 85% of patients with autism,1,5,6 and almost half of all autistic patients are functionally mute.5