First sign you're going crazy when studying:
You start to read your lectures in the accents of the lecturer. Right now I'm doing it in my head, but I'm sure as soon as I get a bit nuttier I'll start doing it out loud. My medical school seems to have a thing for hiring South Africans - so right now I'm learning about pediatric upper airway obstruction in a lovely South African accent. How come they say trachea so weird? (i.e. Truck-eee-a). It kind of makes me giggle.