Study estimates rate of autism spectrum disorder in adults in England

Among children and adolescents, in England, recent surveys have reported an ASD prevalence of approximately ten per 1,000, which is higher than some earlier studies estimating prevalence of 4.4 per 10,000 population and 12.7 per 10,000 population. "It is not known whether this reported increased prevalence reflects case finding changes or increasing incidence due to newly emerging causes," the authors stated as context. At the same time, the authors noted a lack of validated information about the rate of ASDs in British adults, possibly because the symptoms may not be obvious in some: "Adults with ASDs are more likely to be recognized and supported if they also have severe intellectual disability; those with higher levels of functioning tend to be overlooked in the community."

Previous research into England's population of adults with ASDs have been largely based on self-reported data, which may affect the results. Traolach S. Brugha, M.D. (N.U.I.), F.R.C.Psych, from the University of Leicester in Leicester, England, and colleagues from other English colleges and the country's National Centre for Social Research, devised a multipart study. The first phase involved a sample of 13,171 households from the 2007 Adult Psychiatric Morbidity Survey in England; 57 percent of those selected (7,461) responded, and researchers used the Autism-Spectrum Quotient self-questionnaire and other measures to select 618 individuals who were interviewed using the Autism Diagnostic Observation Schedule, Module 4 (ADOS-4), and also provided additional information about other factors such as age, sex, marital status, housing status, income, education, employment, and use of government benefits. None of the study participants had previously received an evaluation for or diagnosis of autism.

Using a threshold of ten or greater on the ADOS-4 to indicate a case of ASD, the authors determined that the overall prevalence of autism spectrum disorder in the English population of persons was estimated as 9.8 per 1,000. The rate of ASD among men (18.2 per 1,000) was higher than among women (2.0 per 1,000) and this difference was statistically significant. Although just 19 individuals in the study met the criteria for ASD, these persons were more likely to use government housing assistance and less likely to study at the university level.

The researchers noted that the adult prevalence of ASD they found is similar to the prevalence in children, but also suggest that their findings need to be independently replicated. Further, they state that the "apparently unrecognized" cases they discovered, particularly among socioeconomically disadvantaged persons, are "of potential public health importance."

More information: Arch Gen Psychiatry. 2011;68[5]:459-466.

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