The Mediating Role of Negative Mood Affect in the Relationship Between Perceived Stress and Vulnerability to Insomnia Among Student Pharmacist Shift Workers.

Background: Perceived stress and vulnerability to develop insomnia are closely linked, with negative mood affect playing a key role. Shift workers, particularly student pharmacists juggling academic demands and irregular work schedules, are at heightened risk for stress-related sleep disturbances. While previous studies have explored their direct relationships, limited evidence exists on the dual role of negative mood affect as both a mediator and a non-mediator in these pathways. This study investigates the mediating role of negative mood affect in the relationship between perceived stress and vulnerability to develop insomnia and assesses whether negative mood affect mediates the reverse relationship. Methods: A cross-sectional study was conducted on 86 student pharmacist shift workers at Notre Dame of Maryland University. Participants completed validated self-report measures, including the Perceived Stress Scale (PSS), the Ford Insomnia Response to Stress Test (FIRST), and the Positive and Negative Affect Schedule (PANAS). Mediation analysis using Hayes' PROCESS macro (Model 4) examined the mediating role of negative mood affect in both pathways. Bias-corrected bootstrapping with 5000 iterations calculated confidence intervals for indirect effects, with significance set at p < 0.05. Results: Negative mood affect partially mediated the relationship between perceived stress and vulnerability to develop insomnia. Higher stress levels were associated with increased negative mood affect (b = 0.49, SE = 0.05, p < 0.01), which, in turn, was linked to greater insomnia vulnerability (b = 0.39, SE = 0.04, p < 0.01). The indirect effect was significant (b = 0.19, 95% CI [0.06, 0.33]). In contrast, negative mood affect did not mediate the reverse pathway (p = 0.15). Conclusion: Negative mood affect significantly mediates the relationship between perceived stress and insomnia vulnerability but not the reverse pathway. Interventions targeting emotional regulation may help reduce stress-related sleep disturbances. Longitudinal studies are needed to confirm these findings and refine interventions.