"A Precious Case from Middle Earth": The latest issue of The British Medical Journal has a case report on Smeagol, aka "Gollum". Among their conclusions,

"He fulfils seven of the nine criteria for schizoid personality disorder (ICD F60.1), and, if we must label Gollum's problems, we believe that this is the most likely diagnosis... He is hypervigilant and does not seem to need much sleep. This, accompanied by his bulging eyes and weight loss, suggests hyperthyroidism."

Of course, it could also be the effect of the One Ring, something not yet included in the current ICD-10 (International Classification of Diseases) codes.