Comparing suicide completion rates in bipolar I versus bipolar II disorder: A systematic review and meta-analysis

Bipolar disorder (BD) has a high disease burden and the highest mortality risk in BD comes from suicide. Bipolar disorder type II (BD-II) has been described as a milder form of bipolar disorder; however, extant literature is inconsistent with this description and instead describe illness burden and notably suicidality comparable to persons with bipolar I disorder (BD-I). Towards quantifying the hazard of BD-II, herein we aim via systematic review and meta-analysis to evaluate the rates of completed suicide in BD-I and BD-II.

We conducted a literature search on PubMed, OVID (Embase, Medline) and PsychINFO databases from inception to June 30th, 2023, according to PRISMA guidelines. Articles were selected based on the predetermined eligibility criteria. A meta-analysis was performed, comparing the risk of completed suicide between individuals diagnosed with BD-I to BD-II.

Four out of eight studies reported higher suicide completion rates in persons living with BD-II when compared to persons living with BD-I; however, two of the studies reported non-significance. Two studies reported significantly higher suicide completion rates for BD-I than BD-II. The pooled odds ratio of BD-II suicide rates to BD-I was 1.00 [95 % CI = 0.75, 1.34].

The overarching limitation is the small number of studies and heterogeneity of studies that report on suicide completion in BD-I and BD-II.

Our study underscores the severity of BD-II, with a risk for suicide not dissimilar from BD-I. The greater propensity to depression, comorbidity and rapid-cycling course reported in BD-II are contributing factors to the significant mortality hazard in BD-II.