The more that I learn, the more I realize how much medicine as a field is in its infancy. It is far safer to assume that supposed conditions are real and science just hasn't caught up yet.

Anyway, it appears to be only a matter of time until there is a "provable" test for autism. See, for example: https://molecularautism.biomedcentral.com/articles/10.1186/s...

There are also observable (via fMRI) differences in the brains of people on the spectrum: http://time.com/3614487/fmri-autism-diagnosis/