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Down Syndrome Abstract
of the Month: Feb 2002

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Autistic disorders in Down syndrome: background factors and clinical correlates

Rasmussen P, Borjesson O, Wentz E, Gillberg C
Dev Med Child Neurol 2001 Nov;43(11):750-4

Institute for the Health of Women and Children, Dept of Child and Adolescent Psychiatry, Univ of Goteburg, Sweden

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A study of a clinic-based sample of 25 individuals (12 females, 13 males; age at diagnosis 14.4 years, SD 7.4 years; age range 4 to 33 years) with Down syndrome (DS) and autism spectrum disorders, demonstrates that autism is by no means rare in DS. Results showed that there was a considerable delay in the diagnosis of autism as compared with children with autism who did not have DS. In 11 participants medical factors were identified that were likely to be of importance in contributing to the development of autism, and in four further participants there were factors of possible significance. Such factors include a history of autism or autism-related disorders in first- or second-degree relatives (n=5 participants), infantile spasms (n=5), early hypothyroidism (n=3), evidence of brain injury after complicated heart surgery (n=2), or a combination of these factors. It is important that autism is recognized, identified, and fully assessed in individuals with DS in order for them to receive appropriate education and support.

My comments:

This is a small study, but I'm choosing this one since autism or autistic behaviors in children with DS is a frequent concern in my e-mail. Previous studies in the past decade have placed the incidence of autism in children with DS at anywhere from 5 to 9%. Yet many people persist in the notion that Down syndrome and autism do not co-exist.

In this study, the 25 individuals with DS and autism had all been referred to the child neuropsychiatry unit at a children's hospital in Sweden over a 15 year period. 22 had simple trisomy 21, 3 had mosaic DS. Diagnosis was made by using a rating scale, such as the Childhood Autism Rating Scale or the Austism Behavior Checklist. Interviews were conducted with parents and teachers, and the diagnosis was based on the definition of autism in the DSM-IIIR or DSM-IV.

The authors noted certain possibly significant factors in the development of autism, and these are mentioned in the above abstract. In 10 participants there were no such factors noted as possible importance.

Because the subjects were all referred to this hospital clinic, the group is not "population-based," so we can't draw firm conclusions from the results. Because the authors made no attempt to compare this group to a group of age-matched people with DS and without autism, it's not possible to come away with any solid evidence that any of the mentioned factors have anything to do with the development of autism. However, we see that autism does occur in people with DS, it is an important "complication" when present, and certain complicating factors may be responsible for the development of an autistic condition rather than DS alone being the cause.

Related website: Disability Solutions, vol.3 issues 5-6, covering DS & Autistic Spectrum Disorder

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