This medical journal article treats Gollum as a subject in a scholarly analysis of his disorders:
There is no disorder of the form of thought. He uses neologisms such as "triksy" and "hobbitses." Gollum has nihilistic thoughts, believing that he is a murderer, liar, and thief; although there is some basis in fact for this and he shows little guilt or remorse. He is preoccupied with, and deeply desires, the ring. He has obsessive thoughts but no compulsions, though he would do anything for the ring. He is hostile towards Frodo, the current owner of the ring. He has paranoid ideation about Sauron ("the eye is always watching") and about Samwise Gamgee ("the fat hobbit… he knows"). Gollum has difficulty controlling his thoughts and actions, exacerbated by prolonged contact with the ring. As Gandalf and Frodo have similar symptoms in the presence of the ring, we can attribute this somatic passivity to the ring. There are features of dissociation. Smeagol has separated his personality and is now Gollum as well.
(via Oblomovka)
