Sleep alterations in major depressive disorder and insomnia disorder: A network meta-analysis of polysomnographic studies.

Major depressive disorder (MDD) and Insomnia disorder (ID) are characterized by sleep alterations. To define their polysomnographic profiles, we conducted a Network Meta-Analysis comparing MDD and ID patients versus healthy controls (HCs). The literature search, conducted from 2008 up to January 2023 and following PRISMA guidelines, covered PubMed, Web of Science, Scopus, and Embase databases. We addressed publication bias using funnel plot asymmetry inspection and Egger's test, evaluated statistical heterogeneity with I, and local and global inconsistencies with the separate indirect from direct evidence method and Q between designs, respectively. Pairwise meta-analyses employed a fixed-effects model, while network analysis utilized a random-effect approach. We evaluated 86 ID and 17 MDD studies, comparing sleep parameters for 636 MDDs versus 491 HCs, and 3661 IDs versus 2792 HCs. The network meta-analysis reported that patients with MDD have greater rapid eye movement (REM) sleep duration and REMs density, and lower REM sleep latency compared to IDs. ID patients instead exhibited lower total sleep time and time in bed, and greater wake after sleep onset and non-REM sleep stage 3 than MDD patients. This work emphasized sleep depth and continuity alterations in both MDD and ID, with major involvement of REM sleep in MDD.