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*Based on a paper given at the Nordic Conference on Autism, Copenhagen, August 2003.
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Incidence of autism spectrum disorders: Changes over time and their meaning†
Article first published online: 2 JAN 2007
DOI: 10.1111/j.1651-2227.2005.tb01779.x
Additional Information
How to Cite
Rutter, M. (2005), Incidence of autism spectrum disorders: Changes over time and their meaning. Acta Paediatrica, 94: 2–15. doi: 10.1111/j.1651-2227.2005.tb01779.x
- †
Publication History
- Issue published online: 2 JAN 2007
- Article first published online: 2 JAN 2007
- Received 17 December 2003; Revised 26 March 2004 and 07 June 2004; Accepted 15 June 2004
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Keywords:
- Autism spectrum disorders;
- diagnostic concept;
- incidence;
- measles-mumps-rubella vaccine;
- thimerosal
Abstract
Aim: Several reviews have noted a huge increase in the rate of diagnosed autism spectrum disorders. The main aims of this paper are: 1) to use published empirical findings to consider whether the rise reflects a true increase in incidence, as distinct from the consequences of better ascertainment and a broadening of the diagnostic concept; and 2) to consider how epidemiological data may be used to test hypotheses about possible causal influences, using MMR and thimerosal as examples. Methods: Search of the literature for studies with a large epidemiological base population, systematic standardized screening, a focus on an age group for which diagnostic assessments are reliable and valid, and diagnosis by trained professionals using high-quality research assessments. Also, search of a broader literature to consider the evidence from all epidemiological studies with respect to the hypothesized causal effect of MMR and thimerosal on autism spectrum disorders. Results: The true incidence of autism spectrum disorders is likely to be within the range of 30–60 cases per 10 000, a huge increase over the original estimate 40 years ago of 4 per 10 000. The increase is largely a consequence of improved ascertainment and a considerable broadening of the diagnostic concept. However, a true risk due to some, as yet to be identified, environmental risk factor cannot be ruled out. There is no support for the hypothesis for a role of either MMR or thimerosal in causation, but the evidence on the latter is more limited.
Conclusion: Progress in testing environmental risk hypotheses will require the integration of epidemiological and biological studies.