Epidemiology of autism in adults across age groups and ability levels.

BACKGROUND: The epidemiology of autism in adults has relied on untested projections using childhood research. AIMS: To derive representative estimates of the prevalence of autism and key associations in adults of all ages and ability levels. METHOD: Comparable clinical diagnostic assessments of 7274 Adult Psychiatric Morbidity Survey participants combined with a population case-register survey of 290 adults with intellectual disability. RESULTS: The combined prevalence of autism in adults of all ages in England was 11/1000 (95% CI 3-19/1000). It was higher in those with moderate to profound intellectual disability (odds ratio (OR) = 63.5, 95% CI 27.4-147.2). Male gender was a strong predictor of autism only in those with no or mild intellectual disability (adjusted OR = 8.5, 95% CI 2.0-34.9; interaction with gender, P = 0.03). CONCLUSIONS: Few adults with autism have intellectual disability; however, autism is more prevalent in this population. Autism measures may miss more women with autism.

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.

The Childhood Autism Spectrum Test (CAST): sex differences.

The Childhood Autism Spectrum Test (CAST) (formally known as the Childhood Asperger Screening Test) identifies autism spectrum conditions by measuring social and communication skills. The present study explored the sex distribution of scores. The CAST was distributed to 11,635 children aged 4-9 years in Cambridgeshire primary schools (UK). 3,370 (29%) were returned. The median score was significantly higher in boys (median test, P < 0.001) (Boys, median = 5 (IQR: 3,8); girls, median = 4 (IQR: 2,6)). There was a predominance of boys (n = 81 (79.4%) over girls (n = 21 (20.6%)) amongst those scoring >or= 15. Exclusion of children with ASC did not significantly affect the results. We conclude that different profiles of social and communication skills in boys and girls must be taken into account when measuring these skills in the general population.

Brief report: prevalence of autism spectrum conditions in children aged 5-11 years in Cambridgeshire, UK.

The study aimed to establish prevalence of the broader autistic spectrum, including Asperger syndrome, in 5- to 11-year-olds in Cambridgeshire, UK. Cases of diagnosed autism spectrum condition (ASC) in children who were in Cambridgeshire schools and aged between 5 and 11 years on 31 December 1999 were sought using public records, screening instruments, educational psychology and special educational needs coordinator (SENCO) records. We report a prevalence of ASC in the age group 5-11 years of almost 0.6 percent (57 in 10,000). This is 11 times higher than the rate of classic autism but in line with other recent national and international rates for the broader spectrum. In the responding mainstream schools the prevalence was 0.33 percent. In the responding special school population it was 12.5 percent. The overall sex ratio of the children with ASC replicated findings for classical autism of 4:1 (M:F), but in those children being educated in mainstream schools the sex ratio was 8:1 (M:F).

The CAST (Childhood Asperger Syndrome Test): preliminary development of a UK screen for mainstream primary-school-age children.

The article describes a pilot and follow-up study of the preliminary development of a new tool to screen for Asperger syndrome (AS) and related social and communication conditions (the Childhood Asperger Syndrome Test, CAST) in children aged 4-11 years, in a non-clinical setting. In the pilot study, parents of 13 children with AS and of 37 typically developing children completed the CAST. There were significant differences between the AS and typical sample means. The pilot was used to establish preliminary cut-off scores for the CAST. In the main study, parents of 1150 primary-school-age children were sent the CAST, and 174 took part in the full data analysis. Results suggest that compared with other tools currently available, the CAST may be useful for identifying children at risk for AS and related conditions, in a mainstream non-clinical sample. Further research is ongoing.

Gestalt processing in autism: failure to process perceptual relationships and the implications for contextual understanding.

BACKGROUND: Deficits in autism have been characterised as a bias towards local over global processing. This paper examines whether there is a deficit in gestalt grouping in autism. METHOD: Twenty-five low-functioning children with autism and 25 controls who were matched for chronological age and verbal mental age took part in the study. RESULTS: The autism group utilised gestalt grouping principles (proximity, similarity, closure) significantly less than the controls. Calculating an overall index of gestalt grouping, the autism group performed at chance level. There was also a deficit in identifying certain impossible figures. This pattern was not reflected in a drawing task, in which the autism sample conformed more to gestalt grouping principles than controls (non-significantly). CONCLUSIONS: The results are discussed in terms of a failure in autism to process inter-element relationships that would allow for the appreciation of larger perceptually coherent units that comprise of multiple elements and, consequently, context. The processes are argued to be preattentive.