Just under 1% of adults living in the community in England are estimated to have autism spectrum disorders.

ED FROM Brugha TS, McManus S, Bankart J, et al. Epidemiology of autism spectrum disorders in adults in the community in England. Arch Gen Psychiatry 2011;68:459–65. Correspondence to Traolach S Brugha, Department of Health Sciences, University of Leicester, Leicester General Hospital, Gwendolen Road, Leicester LE5 4PW, England, UK; [email protected] Sources of funding National Health Service Information Centre for Health and Social Care, Department of Health, National Institute for Health Research and Department of Health. ▶ Reference are available only at http://ebmh.bmj.com Brugha and colleagues present the prevalence of autism spectrum disorder (ASD) in adults using a stratifi ed, multiphase random sample survey design from the third national survey of psychiatric morbidity in England. The authors hypothesised the rate of ASDs in early adulthood would be similar to that reported in older children and conclude that the prevalence of ASDs (9.8 per 1000) in adults is similar to recent estimates found in children in the UK. They suggest that this is evidence that ASD prevalence is temporally constant. This study is the fi rst to show the empirical evidence to refute the notion that ASD rates are increasing by associating ASD prevalence and age. It also highlights both the feasibility and importance of studying adult ASD prevalence. Measuring ASD prevalence within any age group is a complex endeavour. The authors are to be commended for demonstrating that an adult ASD epidemiological study is possible and for acknowledging the challenges faced including a small number of total cases identifi ed (n=19), exclusion of adults residing in institutions and adults with severe intellectual disability and low phase 1 response rates (57%). Interpreting their fi ndings, particularly similarities in ASD prevalence in adults to younger birth cohorts, however, remains unsettled. Two recent ASD epidemiological studies in children, for example, suggest that ASD prevalence is at least 0.331–1.692 times higher than those reported by Brugha and colleagues. Study differences such as variation in the methods used for case identifi cation, prevalence estimates based on a weighted number of cases with wide CI and incomplete ascertainment due to non-participation make cross study comparisons diffi cult. Hopefully, the present study represents one of many to explore the epidemiology of ASDs in adults as such studies in children demonstrate how widely prevalence estimates can vary based on methodology, population size and other factors. In summary, more research is needed to support or refute the premise that there has not been some real increase in autism risk over the last three decades. Judith Pinborough-Zimmerman,