Anti-vaccinationists frequently a quote the recent (the last 10 - 15 years) increases in autism as evidence that vaccines cause autism. Since virtually all good science contradicts this idea, it seems there must be another explanation for this apparent increase. One possible explanation is a change in diagnosis - children who are now diagnosed as autistic would have been diagnosed with a different condition 20 years ago. Anti-vaccinationists ask, “where are the hidden hordes?” – the adult autistics who were not diagnosed autistic as children. Because, if increases in autism are merely a change of diagnosis, then there must be numerous adult autistics who were not diagnosed as such as children.
Professor Dorothy Bishop of the University of Oxford, led a recent study to examine this question. The study was published this month in the Journal of Developmental Medicine & Child Neurology, and its conclusion was indeed to suggest that many children who would now be diagnosed as having autism, were in the 1980s and 1990s diagnosed with severe language disorders instead.
From the abstract we can see that Bishop looked at 38 subjects (aged 15 to 31), who had, as children, been diagnosed as having developmental language disorder, rather than autism. She then applied to them, modern tests for diagnosing autism at age 4 to 5 years – tests that involved interviewing both the subjects and their parents. The result was that one third of the subjects met the modern criteria for autism. The interviews with the parents were especially revealing: the subjects’ parents recalled what we would now regard as autistic symptoms appearing in their children when they were very young. The conclusion is that much of the recent rise of autism could be due to a change in the diagnostic criteria.
The result is consistent with this study in Pediatrics from 2006 that showed the growing autism diagnoses from 1994 to 2003 were associated with corresponding declines in other diagnostic categories.
Of course the study needs replicating with a much larger number of subjects than 38, before any firm conclusions can be drawn. But the study’s tentative conclusion is consistent with the total lack of evidence that autism is caused by vaccines. To be sure, the anti-vaccine crowd would have been quick to publicize this study if the results had been negative, but now they will probably ignore the study, or criticize the independence of the study’s authors. That is their normal tactic when faced with studies they don’t like but have no evidence to refute. But what they won’t have are valid criticisms of the actual study, or studies of their own that show there was, in fact, no change in diagnostic criteria.
It would be nice if CNN and Larry King would now have Professor Bishop on to explain her studies to the public, and undo some of the misinformation they recently helped put out. But, again, we can be sure this won’t happen. They get higher ratings showing the idiotic views of “Professor” Jenny McCarthy.
University of Oxford: Rise in autism related to changes in diagnosis