Earlier quoted context omitted.
>So it seems very spooky on its face that somehow thoughts themselves could have a bidirectional relationship with chemistry. There's no scientific reason to believe thoughts affect the chemistry at all. (Currently at least, but I'm not betting money we'll find one in the future). When Scott Alexander talks about feedback loops like bipolar disorder and sleep, he's talking about much higher level concepts. I don't re…
Sure the thoughts can influence your chemical state. Scott even provides an example. Suppose you become so engrossed in your weird idea you start to lose sleep over it... Or start to feel anxious about it. At some point, your induced stress will cause relevant biological changes. Not necessarily directly. PTSD indeed is likely an overload of a normal learning and stress mechanism.
Under that view, the bipolar feedback loop example disappears. The engrossing or psychotic thoughts are not driving the chemistry, they are the chemistry. The whole thing is just a more macro view where you see certain oscillations play out. If the system ultimately damps itself and that "feels like" self control, it was actually a property built into the system from the start.