Mental disease refers, at present, to disorders of perception, cognition, emotion, and behavior.

The disorder may be mild or severe, acute or chronic, and may be attributed to a defect of mind or body or of some unknown combination of the two. A diagnosis of mental illness is the judgment that an individual is impaired in his or her capacity to think, feel, or relate to others. In mild cases, the impairment may intrude on a person’s ability to gain satisfaction from meeting the challenges of everyday life. In se­vere instances, an individual may be thought so dangerous or incompetent that sequestration within a psychiatric facility is necessary, with a resulting loss of rights normally granted to citizens.