Familial traits of bipolar disorder: A systematic review and meta-analysis.

Background: Genetic studies of bipolar disorder (BD) have shown varied results, which is in part because of the heterogeneity of the disorder. Identifying clinical phenotypes of BD could reduce variability and benefit research. Since BD has a robust genetic component, studies can investigate clinical traits that cluster in families to identify phenotypes with a probable genetic basis.

Methods: We conducted a systematic review of the current literature on familial clinical traits of BD. Text screening and data extraction were performed independently by two reviewers, and random effects meta-analysis was used.

Results: Of 1117 unique records, 16 studies met inclusion criteria. These studies indicated 14 potentially familial traits of BD: age of onset (OR: 4.50; 95% CI: [3.25, 6.22]), bipolar type (OR: 2.05 [1.50, 2.79]), lithium response (OR: 3.71 [1.28, 10.82]), polarity at onset (OR: 1.17 [1.03, 1.34]), psychotic features (OR: 2.20 [1.51, 3.20]), mood-incongruent psychosis (OR: 2.52 [1.66, 3.83]), puerperal psychosis (OR: 6.54 [2.55, 16.77]), rapid cycling (OR: 4.95 [0.96, 25.40]), suicide attempt (OR: 1.04 [0.65, 1.67]), alcoholism (OR: 1.53 [1.09, 2.16]), obsessive-compulsive disorder (OR: 3.10 [1.31; 7.09]), panic disorder (OR: 2.69 [1.12; 6.48]), social anxiety disorder (OR: 1.00 [0.39, 2.55]), and specific phobia (OR: 1.94 [0.95; 3.96]). For most traits, tests of heterogeneity were significant and publication bias was likely.

Conclusion: The results of our review and meta-analysis highlight the lack of studies investigating familial clinical traits of BD, despite the need to address heterogeneity. The large degree of variability between studies must be reduced for future research.