One of a group of mental disorders in which the affected person loses contact with reality. Thought processes are so disturbed that the person does not always realise that he or she is ill. Symptoms include DELUSIONS, HALLUCINATIONS, loss of emotion, MANIA, DEPRESSION, poverty of thought and seriously abnormal behaviour. Psychoses include SCHIZOPHRENIA, MANIC DEPRESSION and organically based mental disorders. (See also MENTAL ILLNESS.)