>It's not necessarily caused by anything external. Y

Then how could a drug fix it? We're positing that there is not only a mechanism causing it, but that this mechanism can be manipulated external to their own self/agency/whatever.

I think that it is at least as absurd to posit that you can come up with one chemical substance or another that will alleviate their depression when you dismiss the idea of coming up with a sequence of words spoken to them that might alleviate their depression. It's the conceit that we have a better idea of how their brains work chemically than we do of how their brains work cognitively.

>Then how could a drug fix it?

Many things that are not necessarily caused by anything external can be fixed by drugs. I don't understand your point.

If the problem is brain not working correctly (because some organ is not doing it's job properly) then no sequence of words will make the brain physically fix itself, just like no sequence of words will cure a heart attack.

Of course it depends, and many people just need a correct therapy. I'm not dismissing talking and figuring out the root cause.