Levitt JJ, Tsuang MT
Am J Psychiatry 1988 Aug;145(8):926-36
Until the 1970s, schizophrenia tended to be broadly defined in the United States, and the diagnosis subsumed patients who had affective as well as schizophrenic symptoms. With the introduction of lithium, however, manic-depressive illness became susceptible to treatment and gained attractiveness as a diagnosis. The ambiguous position of patients with schizoaffective disorder became clear. Cross-sectionally they were seen to resemble schizophrenic patients, but longitudinally they were more akin to patients with affective disorder. Numerous studies have attempted to establish that they are diagnostically distinct, but without clear results. The authors suggest that schizoaffective disorder is heterogeneous and that its treatment should be determined by specific indices as to its subtype.