The news coverage of autism is unfortunately dominated by ill-informed attempts to connect it to childhood vaccinations. Behind the hype, however, is a serious issue: diagnoses of the disorder have risen rapidly, while the biology has turned out to be complicated enough to confound early attempts to pin the underlying causes down. Still, progress is being made, and a paper published last week by PLoS Genetics provides a nice opportunity to review the consensus that appears to be emerging within the field. Recent data is reinforcing earlier findings that suggest autism is not a single disorder and doesn’t have a single underlying cause, but instead is the product of a large number of individually minor genetic contributions.

Twin studies have suggested that there is a very significant genetic contribution to autism, with monozygotic (identical) twins sharing the disorder 92 percent of the time, compared to only 10 percent of other twins. The difference in rates also suggests that more than a single gene is responsible; otherwise, the 10 percent figure would be much higher. Indeed, a variety of studies have now identified individual genes that are associated with a tendency to autism. The new study expanded on this work, using a collection of over 900 families in which more than one child has been diagnosed with autism, provided by the Autism Genetic Resource Exchange. Results were also validated against an independent collection of 859 autistic individuals, and about 2,500 healthy controls.

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