Poor sleep quality mediates between depression to fatigue in a university student sample

Objective: Anxiety, depression and fatigue are frequently co-morbid disorders that are often related to poor sleep quality, although the nature of these associations is not well understood. In this study we examined mediation and moderation between anxiety, depression, poor sleep quality and subjective fatigue. Methods: A short survey assessing anxiety, depression, fatigue and sleep was administered to 140 university students. Results: Anxiety, depression and poor sleep quality predicted 48% of the variance in fatigue score. Poor sleep quality mediated (but not moderated) between depression to fatigue, but it did not mediate or moderate between anxiety to fatigue. Conclusions: These results suggest that sleep disturbance may be an important contributor to fatigue in depressed (but not anxious) students. Thus, sleep hygiene training (e.g., reducing ruminations) might be expected to improve fatigue in depressed students, but not necessarily those with a primary anxiety disorder.