Only a quick post this one, I promise. I, like many people, have been following the various studies looking at the prevalence of autism spectrum conditions quite closely over the years. There are literally hundreds of research papers on prevalence out there to choose from; nearly all pretty much saying the same thing - the prevalence of autism spectrum conditions is increasing. We can add a few more papers to the roll call following on from my mammoth post(s) covering the South Korean study, the UK adult study, the Utah data and the others that I have discussed during my short time on (in?) the blogosphere.
First, there was this paper describing the prevalence of autism in Israel between 1986 and 2005 from registry information. I say 2005, but these dates covered the children born. The actual data presented suggested an increase in the prevalence rate from those born in 1986 (1.2 per 1,000 children) to 3.6 per 1,000 for those born in 2003.
Second, there was this paper describing the incidence (note the word incidence) of autism spectrum conditions in Massachusetts, USA. The authors reported that incidence increased from 56 per 10,000 for those born in 2001, to 93 per 10,000 for those born in 2005 - again based on administrative records.
Both these studies are interesting. The Massachusetts (I always seem to think about the Bee Gees song when I say this place) study is particularly interesting because they have used the word 'incidence' over 'prevalence' which implies that the risk of being diagnosed with an autism spectrum condition increased between 2001 and 2005, at least in Massachusetts, USA.
I am not convinced that from the abstract the Israeli study may also have been determining incidence (being based on birth cohort data); but without yet seeing the full-text of the paper, I can offer no more information at this time.