Decomposing depression: on the prospective and reciprocal dynamics of mood and sleep disturbances.

Sleep disturbances are among the most common and debilitating aspects of major depressive disorder. In a sample of unmedicated adults experiencing a current depressive episode (N participants = 99, N data points = 428), the authors examined the longitudinal dynamics of sleep disturbances and mood symptoms across a 17-week acupuncture treatment study using latent difference score structural equation modeling. Results indicated that changes in sleep and mood disturbances could be characterized as a single bivariate system where low levels of mood symptoms lead to increases in sleep disturbances, whereas high levels of sleep disturbance exert a dampening effect on mood symptoms. Movement of the bivariate system toward or away from better outcomes depended on the precise combination of sleep-mood symptoms; without knowing the state and trajectory of both variables, predicting change in either sleep or mood symptoms was limited. The results have implications for better understanding the complexity and reciprocity of sleep-mood associations, as well as the dynamic, time-based predictors of depressive treatment response.