Hallucinations in bipolar disorder: characteristics and comparison to unipolar depression and schizophrenia.

OBJECTIVE: As there is very little research on the topic, we compared the frequency and the type hallucinations among hospitalized patients diagnosed with bipolar disorder (BPD) versus other major psychiatric illnesses.
METHODS: At admission, all patients hospitalized at the Department of Psychiatry at the Freie Universität Berlin (1981-2001) underwent comprehensive assessments using the standardized Association for Methodology and Documentation in Psychiatry (AMDP) system. We used these data to compare risks and types of hallucinations and associated factors by bivariate and multivariate testing in patients diagnosed with BPD, major depression, or schizophrenia.
RESULTS: At admission, the cross-sectional prevalence of current hallucinations among 4972 hospitalized subjects ranked: schizophrenia (61.1%), bipolar mixed (22.9%), bipolar manic (11.2%), bipolar depressed (10.5%), unipolar depressed (5.9%). The most frequent hallucinations across all patients were auditory, followed by somatic and visual hallucinations. There were only minor age or sex differences in risk of hallucinations. Compared with patients diagnosed with schizophrenia, hallucinations among patients with BPD were less severe, more visual and less often auditory. Characteristics of hallucinations were similar among manic and both bipolar- and unipolar-depressed subjects. Among patients with major affective disorders, those with hallucinations were less well-educated, had higher anxiety scores, less insight into the illness, and their hospitalizations averaged 17% longer. Across all diagnoses, hallucinations, particularly olfactory, were significantly associated with delusions. Hallucinations in BPD were most often accompanied by persecutory delusions; delusions of grandeur were least associated with hallucinations.
CONCLUSIONS: This study provides detailed descriptive data regarding the frequency (cross-sectional) and characteristics of hallucinations in a large sample of patients with BPD, major depression or schizophrenia. Our results suggest a link of lower education and the presence of hallucinations in major affective disorders. The significance of this finding, as well as the role of anxiety in hallucinating patients, requires further study.