New data shed light on the recent mysterious rise in the number of kids being diagnosed with autism.
The new research doesn't explain the increase, but it tells us more about it. It shows that the rise in Californian autism diagnoses (reported to the state DDS) over the period 1996 to 2005 was a cohort effect, meaning that the rates of diagnosis have got higher, the later a child was born.
A child who's 10 today (born 2002) has double of the chance of having a recorded diagnosis compared to a 14-year-old born just four years earlier, in 1998.
"That doesn't tell us anything new!" you might object (I did at first). "All that means is that rates have risen, and we knew that already". But actually it does tell us something important. Because the data could have turned out differently; rates could have risen without a cohort effect, if, ...
