Comparing cognitive reserve between patients with bipolar disorder, other psychiatric disorders and healthy controls: a systematic review and multilevel meta-analysis

Abstract

Bipolar disorder; Cognitive impairment; Cognitive reserve

Trastorn bipolar; Deteriorament cognitiu; Reserva cognitiva

Trastorno bipolar; Deterioro cognitivo; Reserva cognitiva

Background Cognitive Reserve (CR) has been proposed as a protective factor against cognitive decline and functional impairment in psychiatric disorders, including bipolar disorder (BD). However, how CR differs between BD, other psychiatric populations, and healthy individuals remains unclear. Objective This systematic review and meta-analysis aimed to evaluate differences in CR between individuals with BD, healthy controls (HCs), at-risk populations, and patients with other psychiatric disorders. Methods Following PRISMA guidelines, we systematically searched PubMed/MEDLINE, Scopus, PsycINFO, and Web of Science for studies assessing CR in BD and control populations, using validated CR measures or proxies (e.g., education, intelligence quotient, occupational status, leisure activities). A multilevel random-effects meta-analysis was performed to compare CR levels between BD and HCs, and BD and other psychiatric disorders. Results Twelve studies (N = 1861 participants) met inclusion criteria. Meta-analytic findings revealed that individuals with BD exhibited significantly lower CR than HCs (SMD = -0.45, 95 % CI: -0.69 to -0.20, I² = 84.5 %), whereas no significant differences emerged between BD and MDD (SMD = -0.23, 95 % CI: -0.49 to 0.03, I² = 41.7 %). Sociodemographic and clinical variables did not significantly moderate CR levels. Conclusion CR is lower in BD compared to HCs, suggesting its contribution to cognitive and functional impairments. Conversely, similar CR between BD and MDD highlight shared clinical vulnerabilities. These results underscore the need for targeted interventions to enhance CR in patients with BD. Future research should prioritize standardized CR assessment and investigate modifiable factors contributing to CR development in psychiatric populations.