Thought disorder, according to Wikipedia, “refers to disorganized thinking as evidenced by disorganized speech.” They list about 25 types of disorganized speech. To my own observation, I display the following: circumstantiality, flight of ideas (typical in bipolar mania), neologisms, pressure of speech, semantic paraphasia (this one worries me the most), and word approximations.
I’ve done semantic paraphasia for as long as I can remember. Not often, but from time to time, and it always embarrasses me when I do it because it so clearly indicates an error in thinking.
Circumstantiality, arguably, is one of the basic principles of drama. Wikipedia’s page on circumstantiality describes people “talk[ing] the long way around” to their point. In my recent post on pacing a novel, I give two separate sources describing plot as “taking the long way home.”