Epidemiology of Autism Spectrum Disorders in Adults in the Community in England
Traoloch, B.S., McManus, S., Bankart, J., Scott, F., Purdon, S., Smith, J., Bebbington, P., Jenkins, R., & Meltzer, H. (2011). Epidemiology of autism spectrum disorders in adults in the community in England. Archives of General Psychiatry, 68(5), 459-466.
Reviewed by Chris Manente, MEd
Why review this topic?
The prevalence of Autism Spectrum Disorders (ASD) is an issue that has sparked a great amount of debate in recent years. The majority of discussion and inquiry in this area has focused on increasing estimates of the prevalence of the diagnosis of ASD. At the heart of the discussion are debates as to whether the reported increases are due primarily to changes in diagnostic criteria and an overall greater awareness of ASD, or whether the increase in prevalence reflects a real increase in the prevalence of the disorder, possibly caused by genetic, environmental, or immunological factors. It has been suggested that if the prevalence of ASD is in fact on the rise, the rate of ASD among older adults should be lower than among younger populations. The authors of the current study offer that it is likely to be the first to investigate the potential answer to this compelling question.
What did the researchers do?
The current study utilized a multistage sampling procedure and multistage assessment protocol in assessing the prevalence of ASD among adults within the general population in England. Initially, the results of the Adult Psychiatric Morbidity Survey conducted in England were used to identify the potential places of residence for adults living with ASD. Then, each household identified as being potentially eligible to take part in the study was visited by a member of the research team to verify the presence of at least 1 eligible adult. Of the 13,171 eligible addresses visited, 7, 461 (56.6%) agreed to take part in a phase 1 interview. Of these individuals, 849 were selected for phase 2 interviews, of which 630 (74.2%) actually participated and completed the second round of screening.
What did the researchers find?
The data suggested that there was no evidence of a statistically significant reduction in prevalence of ASD as a function of age. This result may indicate that the causes for Autism Spectrum Disorders may be temporally constant and that the recent apparent rises in prevalence may reflect variations among measurement strategies rather than some new environmental toxin.
What are the strengths and limitations of the study? What do the results mean?
The researchers in the current study designed a means of identifying adults with ASD living in the general population that was both reliable and cost effective. Additionally, the researchers developed a diagnostic instrument similar to those previously used to identify ASD among children to ensure that the results were relevant to their original research question of whether the prevalence of ASD among adults is similar to that which has been observed among children. One of the limitations of this study was that the survey used to identify adults with ASD was not appropriate for those individuals with profound disability. Although the researchers note that this particular population represents a small percentage of the overall population of adults with ASD, it may be important for future studies concerning the prevalence of ASD among adults to design more sensitive diagnostic tools that are appropriate for identifying those across the spectrum. Overall, the findings suggested that the prevalence of ASD is neither rising nor falling significantly. This study represents an important milestone in shifting perceptions related to the possible causes for the perceived increase in the prevalence of ASD.