| The highly competent researchers have to answer the question: “why have the number of children diagnosed with ASD increased?” They can’t “control” for changing diagnostic rules: that would literally mean “controlling” the exact thing they’re trying to analyze. What they are doing (as medicinal chemists?) is identify a compound(s) that correlate with the increased diagnoses. Another study might investigate the method by which ASD is diagnosed - eg applying modern diagnoses to old diagnoses, and vice versa. There are also definitely sociological factors that could contribute - in the US specialized educational support for kids diagnosed with ASD is much better funded per-capita than most other learning difficulties, so there is a clear advantage to pushing for (or shopping around for) a dr that will give an ASD diagnosis - eg If you can get FAS diagnoses as ASD you’ll get much more financial and educational support. Personally I expect there to be a parental age component (which would explain the increased prevalence, relative to overall average, of ASD in middle and upper class Caucasian families, at least in the US). I suspect however it’s going to be a combination of all those factors, and probably a few more for good measure. |