Autism and related conditions are more common than was thought, affecting 1 per cent of children.

There is a growing belief that autism and autistic spectrum disorders such as Asperger's are more common that once believed. To provide reliable data, Gillian Baird and colleagues have carried out an in-depth survey of more than 50 000 children aged nine to ten in the South Thames area, in research funded by the Wellcome Trust and the Department of Health.

Within that group, 255 children had already been diagnosed with some kind of autistic spectrum disorder and a further 1515 with special educational needs were screened as 'high risk'. A detailed assessment of a stratified sample of these cases was used statistically to estimate that the population prevalence of childhood autism was 38.9 per 10 000 and that of related conditions was 77.2 per 10 000, or a total prevalence of 116.1 per 10 000 (just over 1 per cent).

This is significantly higher than previous estimates – though it remains unclear whether this reflects an increase in the prevalence of autism and autistic spectrum disorders over time or just better diagnosis.

External links

• Baird G et al. Prevalence of disorders of the autism spectrum in a population cohort of children in South Thames: the Special Needs and Autism Project (SNAP). Lancet 2006;368(9531):210–5.