has features from schizophrenia and affective disorders; symptoms from both can present together or in an alternating fashion. The course may vary from exacerbations and remissions, to one of a long-term deteriorating course. Mood-incongruent psychotic features in a mood disorder is likely to indicate a poor prognosis; this may be true for schizoaffective disorder as well. Prognosis is stated as intermediate between that of patients with schizophrenia and those with mood disorders (Kaplan, Sadock, & Grebb, 1994).
Lifetime prevalence of the disorder is less than 1 percent. Prevalence is reported lower in men and age of onset for women is later than for men. Men are likely to exhibit antisocial behavior with flatness or inappropriateness of affect. Causes are unknown but include the following theories, that schizoaffective disorder may be: a type of schizophrenia or a type of mood disorder; an expression of both; a third type of psychosis; or a heterogeneous group of disorders with all three possibilities. Genet
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