The term lycanthropy was also applied to those individuals afflicted with a form of dark melancholy, a deep depression that gave rise to a violent form of insanity.
Clinical lycanthropy or Lycanthropic Disorder is a form of psychosis or dementia in which the patient has delusions of being a wild animal (usually a wolf). The subject does not actually change shape, but is nevertheless capable of being as dangerous as an actual werewolf.
Many cases of supposed werewolfry victims, which are the works of Lycanthropic Disorder, have been recorded since antiquity. The Book of Daniel describes King Nebuchadnezzar as suffering from depression that deteriorated over a seven-year period into a frank psychosis at which time he imagined himself a wolf.
Among the first medical descriptions were those of Paulus Aegineta during the later days of the Roman Empire. In his description of the symptom complex, Aegineta made reference to Greek mythology in which Zeus turned King Lycaon of Arcadia into a raging wolf.
Thereafter, references to lycanthropy appeared in the ancient literature. The older writers, as Forestus and Burton, regard the werewolf mania as a species of melancholy madness, and some do not deem it necessary for the patient to believe in his transformation for them to regard him as a lycanthropist.
In his Anatomy of Melancholy (1621), Robert Burton writes that those men and women who are suffering from an advanced form of melancholy that graduates into werewolfism lie hidden throughout the daylight hours, then “go abroad in the night, barking, howling, at graves… they have unusually hollow eyes, scabbed legs and thighs, very dry and pale.