A Multiple Mediator Model of Depression, Dysfunctional Beliefs about Sleep, and Sleep Effort in the Relationship between Psychological Inflexibility and Insomnia in Shift Working Nurses.

The aims of this study were to explore the influence of shift working nursing professionals' psychological inflexibility on their level of insomnia. Additionally, we investigated the mediation effect of depression and sleep-related cognitions on this association. An online survey was conducted among 202 nursing professionals at Asan Medical Center from July to August, 2023. Participants responded to questionnaires including the Insomnia Severity Index (ISI), Acceptance and Action Questionnaire-II (AAQ-II), Dysfunctional Beliefs and Attitudes about Sleep - 16 (DBAS-16), Glasgow Sleep Effort Scale (GSES), Patient Health Questionnaire-9 items (PHQ-9), and the Discrepancy between desired time in bed and desired total sleep time index (DBST index). Pearson's correlation and linear regression were performed to explore the factors predicting ISI scores. Mediation analysis was implemented. Linear regression revealed that insomnia severity was predicted by DBAS-16 (β = 0.15, p = 0.008), GSES (β = 0.48, p < 0.001), and PHQ-9 (β = 0.26, p < 0.001). Mediation analysis showed that the relationship between the psychological inflexibility of shift-working nursing professionals' and insomnia severity was fully mediated by depression, dysfunctional beliefs about sleep, and sleep effort. Psychological inflexibility does not directly influence insomnia severity, but depression, dysfunctional beliefs about sleep, and sleep effort fully mediate the relationship.