Psychotic symptoms were present in more than 50% of patients with bipolar disorder across global studies, whereas comorbid schizophrenia diagnoses occurred in about 8% of patients, according to a meta-analysis.
In the study, investigators analyzed the data from 285 studies identified through the Medline, Psych INFO, and Web of Science databases. The studies included 337,993 patients for psychosis outcomes and 206,750 for schizophrenia comorbidity. Prevalence estimates were calculated using single-proportion meta-analysis with random effects models and double arcsine transformation to account for variance across the studies.
The pooled prevalence of comorbid schizophrenia in patients with bipolar disorder was 8% after exclusion of an outlier, with substantial heterogeneity across the studies. Broader psychotic features were more common. Mood-incongruent psychosis was observed in 47% of patients, and lifetime psychosis was observed in 53% of them.
Subgroup analyses showed notable differences by bipolar subtype. Lifetime psychosis occurred in just under 63% of the patients with bipolar I disorder compared with about 17% of those with bipolar II disorder. Psychosis was also more frequent during manic episodes compared with depressive episodes (approximately 70% vs 43%). Current or recent psychosis was reported in 41% of the patients with bipolar disorder, with higher prevalence in bipolar I disorder compared with in bipolar II disorder (approximately 48% vs 7%).
Specific psychotic symptoms were also common. For instance, the lifetime prevalence of delusions was slightly more than 55%, compared with just over 31% for hallucinations and neary 30% for thought disorders. Current symptom prevalence was lower but remained substantial, including about 47% for delusions, 20% for hallucinations, and 22% for thought disorders. Delusions were more frequent compared with other psychotic symptoms across the analyses.
Meta-regression analyses identified clinical and demographic contributors to variability. Bipolar I subtype and manic episodes were consistently associated with higher psychosis prevalence. Male sex was associated with an increased likelihood of comorbid schizophrenia and psychosis, and younger age was linked to higher rates of current psychosis in some subgroups.
The investigators noted several limitations. Heterogeneity was high across all analyses, with I-squared values ranging from approximately 95% to 99%, and only partially explained by factors such as bipolar subtype, age, and gender. Variability in diagnostic criteria, assessment tools, and design likely contributed. Some subgroup analyses were based on small numbers of studies, limiting interpretability.
“[L]ifetime psychosis is present in approximately three out of five [patients with] bipolar I and nearly [one]-fifth of [patients with] bipolar II,” wrote lead study author Wen Shao, of the Department of Psychology at the University of Sheffield, and colleagues.
The authors reported no conflicts of interest.
Source: Bipolar Disorders
