Clinical Vampirism is a psychological condition in which there is a fixation on blood and the delusion of actually being a vampire. The attraction to blood is primarily erotic in nature and may be accompanied by the idea that its consumption conveys certain powers. Clinical vampirism is believed to develop by way of fantasies involving blood and sexual excitement, usually precipitated by some childhood exposure to blood, which the patient found alluring.
Well known psychiatrist and author Richard Knoll proposed the term Renfield's Syndrome based on Dracula's insect eating thrall, to replace that of clinical vampirism. Used briefly and interchangably with 'clinical vampirism', it is no longer recognised as a diagnostic term by the American Psychiatric Association.
Clinical vampirism/Renfield's usually begins with auto-vampirism, the drinking of one's own blood. The urge is sometimes satisified by this, and its victims typically bear slash marks on their arms or other parts of their bodies where they've cut themselves to draw blood. A related condition is known as SMS or Self Mutilation Syndrome--cutters. Here the primary goal is the cutting itself and to watch ones self bleed. Some cutters drink the blood they draw as well, but these are a minority. Most sufferers of SMS are redirecting feelings of anger, frustration, or emotional pain onto their bodies.
In more sociopathic instances of clinical vampirism/Renfield's, the afflicted may attack animals or people in order to drink their blood. In the most extreme end of the syndrome the they will be satisfied with nothing less than human blood and will take it forcibly, up to and including murder.