0651 Daily Associations Between Insomnia and Depression: Emotion Regulation as a Mediator

Abstract Introduction Insomnia has been shown to prospectively predict depression in longitudinal studies. The mechanisms underlying this relationship have not been fully elucidated. Emotion regulation (ER) has been proposed as a potential mediating mechanism; however, empirical tests of it are limited. This study aimed to examine the within-individual relationship between insomnia and depressive symptoms in a 14-day daily study. It was hypothesized that insomnia symptoms on a given night would positively predict depressive symptoms in the subsequent day via ER. Methods This study was conducted in 60 adults (65% female, age = 18-65 years) with elevated insomnia symptoms (Insomnia Severity Index ≥10). They were asked to fill out morning and evening diaries and wear an actigraph for 14 days. The morning diary measured their sleep parameters in the previous night with the Consensus Sleep Diary. The evening diary measured emotional reactivity with the International Positive and Negative Affect Schedule, ER strategy use with the Emotion Regulation Questionnaire and Cognitive Emotion Regulation Questionnaire, and depression with the Center for Epidemiologic Studies Depression Scale. Multilevel modeling was used to analyze the within-individual associations, controlling for between-individual factors such as age and gender. Results Shorter total sleep time on one night predicted greater next-day depressive symptoms (β = -0.063, SE = 0.009, p = .028). Sleep quality was negatively associated with next-day depression at the between-individual level (β = -0.387, SE = 0.882, p = .003). Negative reactivity partially mediated the relationships between sleep quality and depression (β = -0.463, SE = 0.030, p = .008), total sleep time and depression (β = -0.611, SE = 4.938 , p = .011), and sleep efficiency and depression (β = -0.702, SE = 0.007, p = .002), all at the between-individual level. Conclusion The findings suggest that total sleep time is associated with depressive symptoms on a daily level. They also suggest that one of the facets of emotion regulations, namely negative reactivity, plays a mediating role in the insomnia-depression relationship. Nonetheless, we did not find evidence for the mediating role of ER at the within-individual level. Emotional reactivity and ER strategy use may not vary substantially across days. Support (If Any)