While the claim that there has been a statistical increase in...

While the claim that there has been a statistical increase in the number of diagnosed autism cases in the last two decades is irrefutable, there is more to this than a cursory glance first suggests. It is important to note that when autism was first included in the DSM III (1980), it included six strongly worded/defined criteria which required a subject to exhibit all six before a diagnosis could be confirmed. This changed with DSM IV in 1994, where the 6 stringent criteria evolved into 16, more general criteria of which only 8 must present. Further to this, the number of possible diagnoses relevant to autism (think....types of autism - as part of the Autism Spectrum Disorder, which is often quoted for statistics) changed from 2 to 5 -

- Autism disorder (often referred to as simply "autism")
- Asperger's syndrome
- PDD-NOS (Pervasive Developmental Disorder-Not Otherwise Specified)
- Rett Syndrome
- Childhood disintegrative disorder

and included a new "mild" form that represents 56% of new cases since 1994. This led to an explosion in autism diagnoses in the 1990's for obvious reasons. I suspect greater public awareness through traditional and social media through the 00's have also led more parents to have their children tested.....so it is possible that the high rates were there all along.

..........or not. I'm not really commenting either way on whether there are environmental factors at play, just that there are lots of things to consider when looking at the statistics.