Sleep and optimism: The chicken or the egg? A longitudinal study of causal relationships and mediators in a Chinese student sample

Objective. While both sleep and optimism have been found to be predictive of physical and psychological well-being, very few studies have examined their relationship with each other and the potential mediators of their link. This study investigated the cause-and-effect relationship between sleep quality and optimism, as well as the role of symptoms of depression, anxiety, and stress in the relationship.
Method. Internet survey data were collected from 1,684 full-time university students (67.6% female, 84.7% Hong Kong residents, mean age=20.9) at three time-points, spanning about 19 months. Measures included a Chinese attributional style questionnaire (for the measurement of optimism), the Pittsburgh Sleep Quality Index, and the Depression Anxiety Stress Scale.
Results. Moderate correlations among sleep quality, depressive mood, stress symptom, anxiety symptom and optimism were found in cross-sectional analyses. Moreover, bidirectional effect between optimism and sleep quality was shown in cross-lagged analyses. Path analysis demonstrated that anxiety and stress symptoms partially mediated the influence of optimism on sleep quality, while depressive mood partially mediated the influence of sleep quality on optimism.
Conclusion. Findings from our students’ sample showed that optimism and sleep were both cause and effect of each other. While depressive mood partially explained the effect of sleep quality on optimism, whereas anxiety and stress symptoms were one of the mechanisms bridging optimism to sleep quality. This was the first study examining the complex relationships among sleep quality, optimism, and mood symptoms altogether longitudinally in a student sample. Clinical implications on prevention and intervention for sleep problems and mood disorders are discussed. Copyright © 2016 The 4th International Pediatric Sleep Association Congress.