1098 Perceived Social Support Buffers the Association Between Insomnia Severity and Depressive Symptoms in Night-Shift Workers

Abstract Introduction Insomnia and depression have a well-established bidirectional relationship, and both are highly prevalent in night shift workers. Yet, some with severe insomnia do not report high depressive symptoms, suggesting underlying resilience factors. One example is perceived social support; the subjective feeling that reliable help is available. Social support, a buffer against depressive symptoms, may be less accessible to night-shift workers due to inverted schedules. We assessed whether perceived social support moderated the relationship between insomnia severity and depression symptoms in night shift workers and hypothesized that higher social support would be protective. Methods Night shift workers (N = 63) completed the Insomnia Severity Index (ISI), Patient Health Questionnaire-9 (PHQ-9), Epworth Sleepiness Scale (ESS), and a single-item measure of perceived social support ("How often is social support available to you if you need it?") Social support responses were categorized into two groups: Low/Some Support versus High Support. We used a linear regression model to assess whether the interaction between ISI-D and social support (Low/Some vs High) predicted PHQ-9 scores, adjusting for age and gender. Results Higher insomnia severity predicted greater depressive symptoms (β = 0.94, p < .001). Perceived social support significantly moderated this association in both unadjusted models (β = −0.47, p = .019) and models controlling age and gender (β = −0.46, p = .025). Simple slopes indicated insomnia and depression were more strongly associated for those with Low/Some Support (β = 0.94, p < .001) than those with High Support (β = 0.48, p < .001). Conclusion Perceived social support buffered the depressive impact of insomnia severity in night shift workers, highlighting subjective feelings of social support as a meaningful resilience factor. These findings suggest that interventions targeting social support may be a promising avenue for improving mental health in shift-work populations. Future studies should determine whether perceived or objective support (e.g. quantity of social interaction) is most protective, and whether enhancing support can reduce depression risk in shift workers. Support (if any) Support for this study was provided from the NIH R01HL160870 awarded to Dr. Philip Cheng.