Schizoaffective disorder afflicts patients having schizophrenic and affective symptoms. Either they have affective symptoms of sufficient severity and chronicity to exclude an uncomplicated diagnosis of schizophrenia, or they show features of schizophrenia that are sufficient to exclude an uncomplicated diagnosis of an affective disorder. These types of symptoms may or may not occur simultaneously, which underscores the importance of viewing the illness in longitudinal as well as cross-sectional terms. That is, symptom clusters that are primarily affective or primarily schizophrenic may predominate at different times.
Compared with patients with schizophrenia, patients with schizoaffective disorder tend to demonstrate relatively high levels of premorbid function. One of the most common features of the disorder is a precipitating event, such as a life stressor. For example, Tsuang et al.(1) found a higher percentage of such events in schizoaffective disorder (60 per cent) than they did in either schizophrenia (11 per cent), mania (27 per cent), or depression (39 per cent). Marneros et al.(2) also found a higher percentage of precipitating events in schizoaffective disorder (51 per cent) than in schizophrenia (24 per cent), but did not detect a difference between schizoaffective disorder and affective disorder. The nature of the precipitating stressor may vary widely; for instance it may be either physical (e.g. recently giving birth or experiencing a head injury) or interpersonal (e.g. change in an important relationship). The clinical course of the disorder is often characterized by a periodic rapid onset of symptoms that shows a relatively high degree of remission after several weeks or months. As Vaillant pointed out in the 1960s, many of these patients 'recover' completely after an episode, and resume their lives at a premorbid level of function. (3) As will be considered in more detail below, the clinical features of some cases of schizoaffective disorder mainly resemble those of schizophrenia, while the features of other cases are more similar to those of an affective disorder. Regardless of the subtype or variant of the disorder, however, the mortality rate is of special concern. Rates of death, due mainly to suicide or accident, show elevations in this disorder similar to those observed in schizophrenia and in major affective disorders. (4)
In general, the disorder is more common in females than in males. (1,5) The age of onset varies, but tends to be younger than that of unipolar or bipolar disorder. Tsuang et al.(1) found the median age of onset for schizoaffective disorder was 29 years, which was significantly lower than groups with bipolar or unipolar affective disorder, but similar to a group with schizophrenia. Marneros et al.(6) also reported that a median age of onset of 29 years for schizoaffective disorder was lower than the median age for groups with affective disorders (35 years), but also reported that it was higher than a group with schizophrenia (24 years). To an extent, relative differences in the age of onset between schizoaffective and other disorders reflects differences in the diagnostic criteria employed and the heterogeneity of the disorder.
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