OK, so it's well known to LBRB readers that I don’t think it's ever been scientifically established that there has been such a thing as an autism epidemic, but even so, looking at why autism numbers have changed over a certain period of time – the period of time people believe is part of the "epidemic" – should be a good way to determine what contributed to that time period's rise in autism.
Diagnostic changes are the most important influence. After 1987, the definition of autism used in California was broadened several times. Bearman and his colleague Marissa King examined the medical records of around 7000 Californian children with autism and found that one in ten had initially been diagnosed with mental retardation. Extrapolated to the state as a whole, they estimate that this change in diagnosis created almost 5000 extra cases of autism between 1993 and 2005, or 26 per cent of the increase of recorded over that period.
Social influence accounts for another big chunk of the overall increase. Parents are more aware of the disorder than they used to be, and so those whose children who have mild forms of autism have become more likely to seek out diagnosis.
Bearman and his colleague Ka-Yuet Liu quantified this effect. They first estimated how the chances of a child being diagnosed with autism increase if he or she lives close to a child that has already been diagnosed. They then plotted the addresses of children with and without autism in California to calculate the number of children who had grown up close to a child diagnosed with the condition. They were then able to calculate the fraction of extra cases that would have been diagnosed as a result of social interactions. They put this figure at 16 per cent.
The final contribution to the rise in diagnoses comes from demographics. Couples in California are having children later in life, as they are in much of the rest of North America and Europe. That is pushing up autism rates, because autism is triggered by genetic mutations that older parents are more likely to pass on to their children.
Bearman and King calculated that these older parents are responsible for 11 per cent of the extra autism cases.
So, these total 53% of the so-called "epidemic." What about the missing 47%? Well, Professor Roy Grinker says:
Autism used to be highly stigmatised, in part because it was thought to be due to poor parenting. The removal of that stigma has made doctors and parents more willing to recognise the disease, which will have contributed to [some of] the extra cases…This and other social causes, together with uncertainty in the number of cases that can be attributed to the factors already studied by Bearman, could account for much or all of the unexplained half.
But note Grinker doesn’t say it definitely does. This is because he knows as a careful scientist it hasn’t been looked at.
So what can we take from Bearman’s work? In my opinion, we can take the fact that as soon as the questions regarding non-environmental causes were actually looked at and studied, there were numerical values that could be applied to their contribution. There are other non-environmental causes which Bearman didn’t look at, which would probably be found to contribute to the other half.
What about the alleged environmental causes? It would not surprise me in the least if it were found that there were some. But as to what they are, the environmental lobby are still so hung up on vaccines that they don’t seem to want to look at other possible environmental issues. Maybe it's time they dropped the vaccine nonsense and got involved in some decent research. Just a thought.