1) Psychiatric illness or diseases manifested by breakdowns in the adaptational process expressed primarily as abnormalities of thought, feeling, and behavior producing either distress or impairment of function.

2) Broad class of abnormalities of thought, feeling, and behavior, resulting in distress or impairment.

3) A mental or bodily condition marked primarily by sufficient disorganization of personality, mind, and emotions to seriously impair the normal psychological functioning of the individual.