Background: Euthymic bipolar disorder (BD) is associated with general and domain-specific cognitive impairment, which predicts poor occupational and social functioning.
Methods: We searched Embase, Medline, and PsycInfo for articles published between database inception and June 2024, examining cognitive domains in euthymic BD. We conducted meta-analysis, meta-regressions, including premorbid IQ, demographic, and clinical variables. Newcastle Ottawa Scale, I2 statistic, and funnel plots/Egger's and Begg's Test were used to assess quality, heterogeneity, and publication bias, respectively. The Benjamini-Hochberg (BH) procedure was utilised for multiple comparisons.
Results: We identified 95 groups from 75 studies (N = 4,404 BD & 4,037 HC). BD showed significant impairment in general cognitive functioning (Hedge's g = -0.58, 95%CI: -0.79, -0.37, p <.01), verbal memory (Hedge's g = -0.70, 95%CI: -0.79, -0.60, p <.01), executive function (Hedge's g = -0.69, 95%CI: -0.78, -0.60, p <.01), visuo-spatial memory (Hedge's g = -0.68, 95%CI: -0.83, -0.53, p <.01), attention/processing speed (Hedge's g = -0.64, 95%CI: -0.75, -0.54, p <.01), working memory (Hedge's g = -0.61, 95%CI: -0.74, -0.49, p <.01), and premorbid IQ (Hedge's g = -0.24, 95%CI: -0.36, -0.12, p <.01). Demographic and clinical factors were not associated with cognitive performance, except for a statistically significant, but small positive correlation between years of education and lower impairment in verbal memory, β = .066, adjusted p <.05.
Conclusions: Our findings highlight cognitive domains impaired in euthymic BD, indicating targets for interventions. Substantial variance is unexplained, warranting focus on larger samples of individual-level data.
Keywords: bipolar disorder; cognitive functioning; euthymia; meta-analysis; systematic review.