Author ORCID Identifier

Defense Date


Document Type


Degree Name

Master of Science



First Advisor

Bruce Rybarczyk, PhD, LCP

Second Advisor

Joseph Dzierzewski, PhD


Although there is robust empirical support that poor sleep contributes to declines in mental health, explanations of this relationship remain unclear. The purpose of the present study was to examine the pattern of associations between sleep quality, sleep self-efficacy, loneliness, physical activity, and mental health among U.S. adults across the lifespan, and whether they differed by gender or age group. A structural equation model with invariance analysis was developed and examined data from 2,300 adults (Mage = 44.1, SD = 16.78) participating in the online study Investigating Sleep Longitudinally Across Normal Development (ISLAND). Sleep quality was measured by the RU-SATED and Insomnia Severity Index. Mental health was measured by the GAD-2, PHQ-2, and PANAS. Sleep self-efficacy was measured by the sleep self-efficacy scale. Loneliness was measured by the de Jong-Gierveld Loneliness Scale. Physical activity was measured by a calculation of average amount of moderate to strenuous exercise per week and average proportion of sedentary time. Results revealed a significant direct effect of sleep quality on mental health and indirect effect of sleep quality on mental health via loneliness. Indirect effects of sleep quality on mental health via sleep self-efficacy and physical activity were not significant. Overall, the model was invariant across gender and across age groups, except the direct effect of loneliness on mental health was stronger among young adults relative to older adults. Findings suggest that poor sleep quality was associated with greater loneliness and, in turn, associated with greater severity of mental health symptoms. Further research is needed to delineate directionality and causality among sleep quality, loneliness, and mental health.


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