Characteristics of patients diagnosed with schizoaffective disorder compared with schizophrenia and bipolar disorder

Objectives Information on basic demographic and clinical characteristics of schizoaffective disorder is sparse and subject to sampling bias and low diagnostic reliability. In the present study we aimed to: (i) estimate the demographic and clinical descriptors in schizoaffective disorder patients and (ii) compare the findings with those with schizophrenia and bipolar disorder. Methods To minimize sampling bias and low reliability, we systematically reviewed studies that simultaneously compared schizoaffective, schizophrenia, and bipolar disorder patients. We estimated demographic, clinical, and psychometric characteristics based on weighted pooling, and compared disorders by meta-analysis. We also estimated whether schizoaffective disorder is closer to schizophrenia or to bipolar disorder. Results We identified 50 studies that included 18312 patients. Most characteristics of the 2684 schizoaffective disorder patients fell between those of 4814 diagnosed with bipolar disorder and 10814 with schizophrenia. However, the schizoaffective group had the highest proportion of women (52%), had the youngest age at illness onset (23.3 +/- 3.8years), and had the highest standardized ratings of psychosis and depression. Differences in pooled parameters between schizoaffective versus schizophrenia and versus bipolar disorder subjects were similar. Values for patients with schizoaffective disorders mostly were intermediate between schizophrenia and bipolar disorder. However, the majority of studies showed schizoaffective patients to be more like schizophrenia than bipolar disorder patients in seven out of nine demographic and clinical categories as well as in five out of eight psychometric measures. These results remained similar when we restricted the analyses to studies with psychotic bipolar disorder patients only or to studies using the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IIIR and DSM-IV only. Conclusions The present study provided estimates of important characteristics of schizoaffective disorder as balanced as possible in summarizing the findings from observational studies as unbiased as possible. The results did not support the hypothesis that schizoaffective disorder is primarily an affective disorder. The stronger resemblance of schizoaffective disorder to schizophrenia than to bipolar disorder needs further investigation.