Dimensions of Psychosis in Patients with Bipolar Mania as Measured by the Positive and Negative Syndrome Scale

Background: Psychosis is present in 50% or more of patients with bipolar mania and is commonly evaluated in clinical research by means of the Positive and Negative Syndrome Scale (PANSS). The aim of the present analysis was to investigate the psychotic dimensions of bipolar disorder and its contributing symptoms based on a factor analysis of baseline PANSS scores and to compare them with those identified in studies of patients with schizophrenia and bipolar disorder. Sampling and Methods: Baseline data were analyzed from two 3-week, double-blind, placebo-controlled studies of risperidone monotherapy for acute mania associated with bipolar I disorder (n = 535). Inclusion criteria were a DSM-IV diagnosis of bipolar I disorder with manic features, with or without psychotic features, age ≧18 years, and mean baseline Young Mania Rating Scale scores ≧20. A principal component analysis of the 30 PANSS item scores of the 535 patients with a diagnosis of a manic episode at baseline was conducted. Results: Five factors were extracted by the analysis: anxiety (13.4% of the variance), negative symptoms (12.3%), depression (10.5%), excitement (10.3%), and positive symptoms (8.7%). Similar factors, in particular the negative, excitement, and positive factors, have been identified in patients with schizophrenia. There was an absence of a cognitive factor supporting the notion that bipolar patients may present fewer cognitive symptoms. Conclusion: The results of the present analysis and those of other studies indicate similarities in psychotic symptom domains, as measured by the PANSS, in patients with bipolar mania and schizophrenia. Future analyses will address the effects of treatment on the identified factors.