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Acta Paediatr. 2005 Jan;94(1):2-15.

Incidence of autism spectrum disorders: changes over time and their meaning.

Author information

  • Institute of Psychiatry, Kings College, London, UK. j.wickham@iop.kcl.ac.uk

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 10000. 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.

PMID:
15858952
[PubMed - indexed for MEDLINE]
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