The Economist highlights an explanation for the increasing incidence of autism.

While it is now acknowledged that vaccinations do not create autism, cases have risen significantly.

The rate of diagnosis in Britain is up from 50 per 100,000 in 1990 to 400 per 100,000 today. One popular hypothesis, is the “changing fashion� in diagnosis.

While that is difficult to demonstrate, a paper by Dorothy Bishop and her colleagues from Oxford University in Developmental Medicine & Child Neurology has taken a step towards illustrating this.

She reasoned that people now labelled autistic might have been given another diagnosis in the past. To examine this, she looked at a group diagnosed as children with a condition that was not autism – such as developmental language disorder – and then re-diagnosed them with current criteria.

Having interviewed the volunteer group, and their parents, almost a third had been misclassified.

The interview with the parents was significant with many telling Dr Bishop stories of what are now regarded as “autistic symptoms appearing in their children in their early years.�

While Dr Bishop is cautious, and her early conclusions may need to be the subject of larger studies to confirm her observations, it appears that with her colleagues she has identified and highlighted the cause of the recent rise of autism as being a change in the diagnostic criteria.

The conclusion appears straightforward: It now looks unlikely that there are more autistic people around than there used to be, it is just “that it is now fashionable to acknowledge their existence.�