There are no tests or biological measures that can assist in making the diagnosis of schizoaffective disorder. Whether schizoaffective disorder differs from schizophrenia with regard to associated features such as structural or functional brain abnormalities, cognitive deficits, or genetic risk factors is not clear.
Schizoaffective disorder appears to be about one-third as common as schizophrenia. Life- time prevalence of schizoaffective disorder is estimated to be 0.3%. The incidence of schizoaffective disorder is higher in females than in males, mainly due to an increased in- cidence of the depressive type among females.
The typical age at onset of schizoaffective disorder is early adulthood, although onset can occur anywhere from adolescence to late in life. A significant number of individuals diag- nosed with another psychotic illness initially will receive the diagnosis schizoaffective dis- order later when the pattern of mood episodes has become more apparent. With the current diagnostic Criterion C, it is expected that the diagnosis for some individuals will convert from schizoaffective disorder to another disorder as mood symptoms become less prominent. The prognosis for schizoaffective disorder is somewhat better than the prog- nosis for schizophrenia but worse than the prognosis for mood disorders.
Schizoaffective disorder may occur in a variety of temporal patterns. The following is a typical pattern: An individual may have pronounced auditory hallucinations and per- secutory delusions for 2 months before the onset of a prominent major depressive episode.
The psychotic symptoms and the full major depressive episode are then present for 3 months.
Then, the individual recovers completely from the major depressive episode, but the psy- chotic symptoms persist for another month before they too disappear. During this period of illness, the individual’s symptoms concurrently met criteria for a major depressive ep- isode and Criterion A for schizophrenia, and during this same period of illness, auditory hallucinations and delusions were present both before and after the depressive phase. The total period of illness lasted for about 6 months, with psychotic symptoms alone present during the initial 2 months, both depressive and psychotic symptoms present during the next 3 months, and psychotic symptoms alone present during the last month. In this in- stance, the duration of the depressive episode was not brief relative to the total duration of the psychotic disturbance, and thus the presentation qualifies for a diagnosis of schizoaf- fective disorder.
The expression of psychotic symptoms across the lifespan is variable. Depressive or manic symptoms can occur before the onset of psychosis, during acute psychotic episodes, during residual periods, and after cessation of psychosis. For example, an individual might present with prominent mood symptoms during the prodromal stage of schizo— phrenia. This pattern is not necessarily indicative of schizoaffective disorder, since it is the co—occurrence of psychotic and mood symptoms that is diagnostic. For an individual with symptoms that clearly meet the criteria for schizoaffective disorder but who on further fol- low-up only presents with residual psychotic symptoms (such as subthreshold psychosis and / or prominent negative symptoms), the diagnosis may be changed to schizophrenia, as the total proportion of psychotic illness compared with mood symptoms becomes more prominent. Schizoaffective disorder, bipolar type, may be more common in young adults, whereas schizoaffective disorder, depressive type, may be more common in older adults.
Genetic and physiological. Among individuals with schizophrenia, there may be an in- creased risk for schizoaffective disorder in first-degree relatives. The risk for schizoaffec- schizophrenia, bipolar disorder, or schizoaffective disorder.
Cultural and socioeconomic factors must be considered, particularly when the individual and the clinician do not share the same cultural and economic background. Ideas that ap- pear to be delusional in one culture (e.g., witchcraft) may be commonly held in another.