The idea that mental illness has an organic basis is not new, by the way. It’s just taken a long time for the idea to catch on. Here’s Plato in Timaeus:
The truth is that the intemperance of love is a disease of the soul . . . And in general, all that which is termed the incontinence of pleasure and is deemed a reproach under the idea that the wicked voluntarily do wrong is not justly a matter for reproach. For no man is voluntarily bad; but the bad become bad by reason of an ill disposition of the body and bad education, things which are hateful to every man and happen to him against his will.
I came across this passage in a footnote in an excellent book by philosopher Rebecca Goldstein, titled Plato at the Googleplex.