The apparent rise in autistic people in the last 40 years

Question

I’m curious as to the seeming rise of autistic humans in the last decades.

Is it that it was just not understood and therefore not diagnosed/reported?

Are there environmental or even societal factors that have corresponded to this increase in cases?

In: Biology

Answer 1

A combination of more testing for it, a better understanding of it, and less stigma about it meaning less incentive to hide it if you can. 

Same general idea as the famous graph of number of left-handed people spiking up to 12% after we stopped forcing everyone to learn to write right-handed and stigmatizing left-handedness. The number of left-handed people didn’t grow and was probably always about 12%, but the number of people who reported being left handed increased to nearly everyone who was.