Perceived stress mediates the longitudinal effect of sleep quality on internalizing symptoms

Background: Numerous studies have explored the relationship between sleep quality and internalizing symptoms (i.e., depression and anxiety), but there is uncertainty about their directional pathways. Here, we investigated the longitudinal associations between sleep quality and internalizing symptoms and tested the potential mediation effect of perceived stress. Methods: A longitudinal survey of Chinese healthcare students (N = 343) was conducted at three time points: Time 1 (baseline), Time 2 (1 week later), and Time 3 (3 weeks after Time 2). Participants completed the Sleep Quality Questionnaire (SQQ), Perceived Stress Questionnaire-30 (PSQ-30), and the Patient Health Questionnaire-4 (PHQ-4) at each time point, where each asked about participants' experiences over the past week. A higher SQQ score indicated poorer sleep quality, while higher scores on the PHQ-4 and PSQ-30 indicated more severe internalizing symptoms and perceived stress. Using autoregressive cross-lagged panel modeling (CLPM), we examined the bidirectional relationships among sleep quality, internalizing symptoms, and perceived stress. Results: CLPM revealed that baseline sleep quality negatively predicted subsequent changes in internalizing symptoms, and vice versa. While perceived stress mediated the relationship between sleep quality and internalizing symptoms at the 3-week follow-up (β = 0.017, p = .038), it did not mediate the reverse relationship between internalizing symptoms and sleep quality. Conclusions: There was a negative bidirectional relationship between sleep quality and internalizing symptoms. Furthermore, perceived stress mediated the effect of poor sleep quality on internalizing symptoms, suggesting that good-quality sleep may enhance stress resilience and alleviate symptoms of depression and anxiety, thereby improving overall wellbeing.