Prevalence of autism-spectrum conditions: UK school-based population study.


BACKGROUND: Recent reports estimate the prevalence of autism-spectrum conditions in the UK to be 1%. AIMS: To use different methods to estimate the prevalence of autism-spectrum conditions, including previously undiagnosed cases, in Cambridgeshire. METHOD: We carried out a survey of autism-spectrum conditions using the Special Educational Needs (SEN) register. A diagnosis survey was distributed to participating schools to be handed out to parents of all children aged 5-9 years. The mainstream primary school population was screened for unknown cases. RESULTS: The prevalence estimates generated from the SEN register and diagnosis survey were 94 per 10 000 and 99 per 10 000 respectively. A total of 11 children received a research diagnosis of an autism-spectrum condition following screening and assessment. The ratio of known:unknown cases is about 3:2 (following statistical weighting procedures). Taken together, we estimate the prevalence to be 157 per 10 000, including previously undiagnosed cases. CONCLUSIONS: This study has implications for planning diagnostic, social and health services.