ABSTRACT
The positive symptoms appear to reflect an excess or distortion of normal functions, whereas the negative symptoms appear to reflect a diminution or loss of normal functions. The positive symptoms include distortions or exaggerations of inferential thinking (delusions), perception, language and communication, and behaviour. Continuous signs of the disturbance persist for at least six months. The list of criteria goes on specifically to exclude schizo-affective and mood disorders, substance and general medical disorders, and pervasive developmental disorders. The median age of onset for the first psychotic episode of schizophrenia is in the early to mid-twenties for men and in the late-twenties for women. The course and outcome in schizophrenia are variable. The essential feature of this type is the presence of prominent delusions of a persecutory nature and/or auditory hallucinations while cognitive functioning and affect remain relatively unaffected.
