Executive functions and memory in bipolar disorders I and II: new insights from meta-analytic results

Objective: To perform a systematic review and meta-analysis of executive functions (EF) and episodic memory in bipolar disorder (BD). Methods: A literature search was conducted on three electronic databases. Results were combined using random-effects meta-analysis. Results: A total of 126 studies (6424 patients with BDI, 702 with BDII, and 8276 controls) were included. BDI was associated with moderate to large impairments across all cognitive functions and BDII with small-to-medium impairments. Small significant differences were identified between BDI and BDII on all cognitive functions except inhibition. The Trail Making Test (TMT) (g = 0.74, 95% CI: 0.67–0.80), Hayling Test (g = 0.58, 95% CI: 0.34–0.81), Digit Span Total (g = 0.79, 95% CI: 0.57–1.01), and Category Fluency (g = 0.59, 95% CI: 0.45–0.72) tasks were most sensitive to cognitive impairment in BDI. The TMT (g = 0.65, 95% CI: 0.50–0.80) and Category Fluency (g = 0.56, 95% CI: 0.37–0.75) were also sensitive to cognitive alterations in patients with BDII. Conclusion: BD type I was associated with more severe and widespread impairments than BDII, which showed smaller impairments on all functions except inhibition, where impairments were larger. Education and (hypo)manic symptoms should be further investigated in future studies due to their possible influence on the neuropsychological profile of BD. The instruments identified in this review should be considered for inclusion in cognitive assessment batteries in BD.