Prospective memory in bipolar disorder: A meta-analysis

There are conflicting findings about prospective memory (PM) performance in bipolar disorder. This meta-analysis systematically examined PM in patients with bipolar disorders. Articles were systematically searched in both English and Chinese databases, from their inception to Nov 15, 2016. Only case-control studies on PM in bipolar patients were included for analyses. The random effect model was used in all meta-analytic outcomes. Four studies (n = 390) comparing PM performance between patients with bipolar disorder (n = 208) and healthy controls (n = 182) were included. Three studies were rated as "high quality", while the quality of evidence in 3 meta-analyzable outcomes ranged from "moderate" (67%) to “high” (33%). Compared to healthy controls, bipolar disorder patients showed impairments in overall PM [2 studies, n = 196; SMD: − 1.08 (95%CI: − 1.61, − 0.55), P < 0.0001; I2 = 65%], event-based PM [4 studies, n = 367; SMD: − 0.51 (95%CI: − 0.78, − 0.23), P = 0.0003; I2 = 37%] and time-based PM performance [4 studies, n = 367; SMD: − 0.82 (95%CI: − 1.11, − 0.52), P < 0.0001; I2 = 41%]. In this meta-analysis, both time-based PM and event-based PM deficits appeared to be evident in bipolar disorder.