Why Sleep is Key: Poor Sleep Quality is a Mechanism for the Bidirectional Relationship between Major Depressive Disorder and Generalized Anxiety Disorder Across 18 Years ☆

Abstract

Background Generalized anxiety disorder (GAD) and major depressive disorder (MDD) reliably precede and predict one another. However, there is insufficient data on mediators through which the longitudinal GAD-MDD association unfolds. Based on insomnia theories, such as the hyperarousal model of sleep, we tested the degree to which poor global sleep quality functioned as a mediator of the prospective bidirectional anxiety-depression relationship.

Method Participants were 3,294 community-dwelling adults who partook in three measurement waves nine years apart. The Composite International Diagnostic Interview-Short Form assessed GAD and MDD in-person at baseline (Time 1 [T1]), Time 2 (T2; nine years after T1), and 18 years later (T3). T2 global sleep quality was measured using the multiple-domain Pittsburgh Sleep Quality Index self-report at T2. We used longitudinal structural equation modeling mediation analyses.