Do sleep variables predict mood in bipolar disorder: A systematic review

Most people with bipolar disorder (BD) experience sleep disturbances across mood states and many identify sleep changes before both depressive and manic episodes. Nearly half of all patients have multiple relapses of BD and identifying early warning signs of relapse, such as sleep changes, could benefit both patients and clinicians as a preventive strategy.

A systematic search of the databases Embase, APA PsychINFO, and MEDLINE was performed to identify studies that investigated the relationship between sleep changes and mood in BD. The review was registered with PROSPERO (CRD42023405950) and followed the PRISMA guidelines. Results were categorised based on the identified relationship between sleep changes and mood, e.g. sleep and depression correlation, and these are synthesised narratively. The Newcastle-Ottawa scale was used to assess the risk of bias (RoB).

The systematic literature search yielded 7159 records. 17 publications were included, describing 13 studies. Nine categories were identified describing the relationship between sleep and mood (e.g. sleep-mood correlations and comparing BD and HC on sleep duration). Regardless of sleep assessment (e.g. actigraphy), study duration or mood outcome, changes towards longer sleep, earlier onset and later wake-up were mostly followed by depressive mood, and vice versa for mania. 14 papers had a "fair" RoB rating.

Changes in sleep patterns appear to precede predictable mood changes in BD and could be used as early warning signs for patients and clinicians. The main limitation of the study is the high heterogeneity between study results, preventing the conduction of a meta-analysis.