The prevalence of autism spectrum disorders Recent evidence
and future challenges.
Charman T.
Behavioural and Brain Sciences Unit, Institute of Child Health, 30 Guilford
Street, London, WC1N 1EH, UK. t.charman@ich.ucl.ac.uk
BACKGROUND: Until recently best estimate prevalence rates for autism spectrum
disorders (ASD) were 0.5/1,000 for autism and 2.0/1,000 for the broader
spectrum. Three recent studies have suggested a significantly higher
prevalence rate for ASD of 6.0/1,000 (mean 95 % CI = 4.8-8.0). METHOD:
Possible determinants of the apparent increase in the prevalence of ASD are
outlined. Methodological aspects of the three recent studies are examined.
FINDINGS: Increased recognition, the broadening of the diagnostic concept over
time and methodological differences across studies may account for most or all
of the apparent increase in prevalence, although this cannot be quantified.
CONCLUSIONS: Findings from ongoing studies should help confirm or disconfirm
the putative rate of 6.0/1,000 for all ASD. The possibility that autism has
been over-diagnosed in recent studies needs to be ruled out. Notwithstanding
these outstanding questions, it appears likely that the current true
prevalence of ASD is considerably greater than previously recognised. This has
significant implications for our scientific understanding of ASD and for
families and services. Future directions for epidemiological research are
outlined.
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