QUESTION: Recent data suggest that anxiety disorders are as often comorbid with bipolar disorder (BD) as with unipolar depression. The literature on panic disorder (PD) comorbid with BD has been systematically reviewed and subject to meta-analysis.STUDY SELECTION AND ANALYSIS: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were thoroughly followed for literature search, selection and reporting of available evidence. The variance-stabilising Freeman-Tukey double arcsine transformation was used in the meta-analysis of prevalence estimates. Both fixed-effect and random-effects models with inverse variance method were applied to estimate summary effects for all combined studies. Heterogeneity was assessed and measured with Cochran's Q and I statistics.FINDINGS: Overall, 15 studies (n=3391) on cross-sectional prevalence and 25 independent lifetime studies (n=8226) were used to calculate pooled estimates. The overall random-effects point prevalence of PD in patients with BD, after exclusion of one potential outlier study, was 13.0% (95% CI 7.0% to 20.3%), and the overall random-effects lifetime estimate, after exclusion of one potential outlier study, was 15.5% (95% CI 11.6% to 19.9%). There were no differences in rates between BD-I and BD-II. Significant heterogeneity (I >95%) was found in both estimates.CONCLUSIONS: Estimates that can be drawn from published studies indicate that the prevalence of PD in patients with BD is higher than the prevalence in the general population. Comorbid PD is reportedly associated with increased risk of suicidal acts and a more severe course. There is no clear indication on how to treat comorbid PD in BD. Findings from the current meta-analysis confirm the highly prevalent comorbidity of PD with BD, implicating that in patients with BD, PD might run a more chronic course.