Dynamic within-person associations between problematic social media use and sleep quality among university students: The mediating role of nomophobia and the moderating role of trait rumination.

Problematic social media use (PSMU) and poor sleep quality are prevalent among university students. Although previous research has documented associations between PSMU and sleep problems, less is known about the short-term dynamic mechanisms underlying this relationship and the individual differences that may shape vulnerability. Drawing on intensive longitudinal data and dynamic structural equation modeling, this study examined a moderated mediation model in which nomophobia (i.e. anxiety or distress arising from being unable to access or use one's mobile phone) mediated the association between PSMU and poor sleep quality, with trait rumination examined as a moderator of this indirect association. A 21-day daily diary study was conducted with 228 Chinese university students. At the between-person level, higher PSMU was associated with greater nomophobia and poorer sleep quality. At the within-person level, increases in PSMU were prospectively associated with greater nomophobia, which subsequently predicted poorer sleep quality, supporting an indirect association through nomophobia. This indirect association was more pronounced among students with higher levels of trait rumination. By capturing dynamic day-to-day processes, these findings extend current understanding of how PSMU may contribute to poorer sleep during emerging adulthood and highlight nomophobia and rumination as potential targets for interventions aimed at promoting healthier digital habits and sleep.