Abstract
BACKGROUND: Sleep hygiene is integral to health, and sleep regularity may be associated with mental health outcomes in addition to duration. Although sleep and depression relationships are well-studied, the relative impact of different sleep factors remains unclear. As patient-specific factors and health behaviors influence sleep and mental health, we investigated associations between sleep and depression severity considering such factors in a United States sample of adults. METHODS: Two cycles (2011-2012, 2013-2014) from the National Health and Nutritional Examination Survey were studied. Objective sleep duration (day and night), and the sleep regularity index (SRI) were calculated from physical activity monitors worn for seven days. Complex survey procedures with four-year weights were used, and backward selection was used to test relevant variables in the fully adjusted regression model. RESULTS: Among participants (n = 7297), we found associations between sleep-associated variables and SRI, with increased daytime sleep being the strongest correlate of decreased SRI. In the fully adjusted model, lower SRI scores and reduced subjective night sleep remained significantly associated with depression. Sex was an additional independent predictor, with females exhibiting higher depression scores, and a significant sex × SRI interaction revealed that the inverse relationship between SRI and depressive symptoms was stronger in females than in males. Health behaviors, including active tobacco and cannabis use, were also associated with increased depression severity in the adjusted model. CONCLUSIONS: Daytime sleep may serve as an SRI proxy, although additional cohorts should confirm relationships. Higher depression severity was associated with different sleep components, emphasizing the importance of sleep hygiene in mental health. Behaviors like current smoking and cannabis use were also associated with increased depression. Research exploring the temporality and interactions between these factors may assist in non-pharmacologic depression treatment.