1 in 100, Part 1

by Benison O'Reilly on Wednesday, October 7th, 2009

Studies published in the last month on both sides of the Atlantic point to an ASD prevalence of around 1 in 100.  Whilst the US research in children (to be discussed in a future blog) has provoked familiar cries of an ‘autism epidemic’, the British research was actually conducted in adults and supports what some researchers have been saying for years:  autism spectrum disorders have always been with us, but our recognition of them has grown immeasurably in recent years.

The official title of the report is: Autism Spectrum Disorders in adults living in households throughout England: Report from the Adult Psychiatric Morbidity Survey 2007 and it’s available for all to read at the NHS Information Centre: www.ic.nhs.uk/

As the title implies, the ASD research was part of a larger study on psychiatric morbidity. A random sample of adults aged 16 years and older was screened for ASD using a 20 item version of the Autism Quotient (AQ-20).  A subset of respondents with medium to high AQ-20 scores was selected to take part in a phase two interview, where assessments were carried out by clinically trained interviewers using the Autism Diagnostic Observation Schedule (ADOS). The results were weighted to generate a prevalence rate for the population as a whole.

Using a recommended threshold score on the ADOS, 1.0% of the adult population was assessed as having an ASD (i.e. Autistic Disorder, PDDNOS or Asperger’s Syndrome). The rate was higher in men (1.8%) than women (0.2%), consistent with childhood population studies.

Other findings included:

People who were single were more likely to be assessed with ASD.

The rate of ASD was lowest among those with a degree level qualification (0.2%) and highest among those with no qualifications (2.1%).

Those living in accommodation rented from a social landlord were the most likely to have ASD.

Being of low predicted verbal IQ was also associated with presence of ASD.

There was no indication of any increased use of treatment or services for mental or emotional problems among people with ASD (the implication being that they were underutilising services, not that they didn’t need them).

Because of the small sample size, the investigators advise caution interpreting the population distribution of ASD (particularly among women) but the results are interesting in that they suggest that rates of autism are broadly consistent across the age groups; that is, it’s as much a disorder of adults as it is of children.

On a personal note, I can’t help wondering how many adults on the spectrum are out there, not feeling all that ‘disabled’ and just quietly getting on with their lives.

Tags: autism, prevalence, research