Validity of the negative/positive dichotomy for schizophrenic disorders under long-term conditions.

A total of 148 patients fulfilling the DSM-III symptomatological criteria of schizophrenia were classified according to Andreasen's criteria of positive, negative and mixed symptomatology. After excluding cases of permanent hospitalisation and patients with monoepisodic course the remaining 100 patients had a total of 458 episodes. Of these episodes, 213 were identified as positive, 134 as negative and 111 as mixed. During the course of illness the proportion of negative episodes increased and the proportion of positive episodes decreased. The great majority of the patients (76%) had a bimorphous course, i.e. one showing both types of schizophrenic symptomatology, positive and negative. Only 6% of the patients had only negative episodes, and only 18% had only positive episodes. The shift from one type of episode to another is dependent on the length of illness. Stability was not greater later during the course of illness than at the beginning.