[Comorbidity in autism spectrum disorders - I. Mental retardation and psychiatric comorbidity]

Recent epidemiological surveys show a higher prevalence of autism spectrum disorders than was to be expected based on the first studies in this field. The objective of our study is to analyse the frequency of mental retardation and co-morbid psychiatric disorders and symptoms in a large clinical sample of patients with pervasive developmental disorders.

The sample consists of all patients (N = 601) with a pervasive developmental disorder diagnosed at the Department of Developmental Disorders at the Heckscher-Klinikum. For all patients the level of intellectual functioning was measured. In addition to psychiatric diagnoses, we also recorded intervention-relevant symptoms such as eating and sleeping problems, and auto-aggressive behavior on Axis I, as well as psychosocial impairments and level of psychosocial functioning on Axes V and VI.

26% of the patients functioned on a normal intellectual level (N = 58). 54% of the patients (N = 325) had at least one additional psychiatric diagnosis, and 19% (N = 110) had two additional diagnoses. The most frequent diagnoses were externalizing disorders (N = 221). Internalizing disorders (N = 96), as well as other disorders (N = 114) were about equally frequent. Auto-aggressive behavior occurred more often among children with severe mental retardation than in children of normal intelligence. There was a significant association between the presence of (auto-)aggressive behavior as well as externalizing diagnoses and the level of psychosocial functioning.

Children with pervasive developmental disorders show a wide variety of co-morbid problems, which are relevant for the treatment and the course of the disorder. The presence of externalizing behaviors is an additional burden on the development of these children.