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Individuals who have multiple children with autism have more severe social and communication deficits than either controls or those who have only one child with autism, according to a study published 8 September in Autism Research1.
The results support the theory that the broad autism phenotype, which describes autism-like features in the family members of individuals with autism, has a genetic basis.
Studies of children with autism from so-called multiplex families, which have more than one child with the disorder, usually uncover genetic variants that are likely to be inherited and that lead to autism in combination with other mutations or environmental factors. By contrast, studies of simplex families, which have only one child with autism and unaffected siblings and parents, often identify more harmful spontaneous, or de novo, mutations that are not present in either parent.
In the new study, researchers used a measure called the Broader Phenotype Autism Symptom Scale (BPASS) to rate social skills, conversational ability and repetitive behavior in 39 multiplex parents, 22 simplex parents, 20 parents of children with a developmental disability and 20 parents of typically developing children. The researchers included children with developmental disabilities to account for the stress that the parents of a special-needs child might experience.
Parents of multiplex children have more deficits in the social interest and conversational measures of the BPASS than do simplex parents or controls, the study found. In general, simplex parents have behaviors similar to those of the two control groups.
The BPASS is a relatively new measure of social ability, based on interviews and video observation by trained clinicians. Unlike other measures of social ability in adults, which rely on self-reporting, the researchers do not know whether the parents are in the experimental group or are controls, eliminating potential bias.
The parents in the study earned similar scores even when rated by clinicians who knew which group they belonged to, however, suggesting that BPASS is resistant to bias.
1: Bernier R. et al. Autism Res. Epub ahead of print (2011) PubMed