I’ve just got a copy of Holford and Fiona McDonald Joyce’s Smart Food for Smart Kids (Piatkus: 2007). Holford argues that “A survey of children published in the Lancet
finds that the incidence of autistic spectrum disorders [ASD] has more than doubled in the last 20 years” (p. 11). Holford references Baird et al’s 2006 paper on the subject: a good source, but it doesn’t back up Holford’s claim. Given the current debate around the Observer’s dubious figures on autism rates, this seems a topical claim to address now.
I could engage with Holford stats by going through the figures in the Baird et al paper – I might do so when time allows – but for now it will be sufficient to note a statement in the article’s abstract (I have looked at the full text of the article, but the authors make their position on this quite clear in the abstract). For Baird et al, their paper shows that:
Prevalence of autism and related ASDs is substantially greater than previously recognised. Whether the increase is due to better ascertainment, broadening diagnostic criteria, or increased incidence is unclear.
In other words, Baird et al make it perfectly clear that their research may not show any increase in ASD rates whatsoever: the increase in diagnoses could be down to changes in diagnostic practices. It is therefore potentially misleading – and unnecessarily alarmist – for Holford to cite this article as showing a doubling of ASD rates.