Personal sleep debt and daytime sleepiness mediate the relationship between sleep and mental health outcomes in young adults

Background: Sleep duration and chronotype (i.e., morningness-eveningness) are associated with increased depression and anxiety risk, but differences in individual sleep need and lifestyle may mean these sleep parameters do not present the same risk across all individuals. This study explored the mediating role of sleep debt and daytime sleepiness in the relationship between sleep and mental health symptoms in young adults, a particularly vulnerable population. Methods: Young adult university students (n = 2,218) and young adults from the general population in the United States (n = 992) provided estimates of actual and optimal sleep duration, and completed validated measures of sleepiness, chronotype, and depression and anxiety risk. Mediation models examining sleepiness and sleep debt (i.e., difference between optimal and actual sleep) as parallel mediators were tested. Results: Sleepiness and sleep debt mediated the relationship between short sleep and depression and anxiety risk in the university sample, while sleepiness mediated these relationships in the general population sample. Sleepiness and sleep debt also mediated the impact of evening-type preferences on depression and anxiety risk in university students, but no mediation of this effect was found in young adults from the general population. Conclusions: This study reports potential mediating mechanisms related to the increased mental health risk conferred by short sleep and evening chronotype. These results have implications for how primary care physicians assess psychopathology risk, arguing for a focus on the assessment of daytime sleepiness and sleep debt in university populations, while for young adults in the general population, these factors may be less important.