Reciprocal relationships among problematic social media use, depression, and social anxiety of Chinese university students: Disentangling between- and within-person effects.

The associations between problematic social media use (PSMU), depression, and social anxiety (SA) remain a topic of debate. Hence, this study investigated the bidirectional longitudinal relationships of PSMU with depression and SA in a sample of Chinese university students, with an additional emphasis on potential sex differences. A total of 378 students (56.3 % male, 43.7 % female; Mage = 20.49 years, SD = 0.65) completed three waves of survey data. Random Intercept Cross-lagged panel model analysis and multi-group analysis by sex were conducted. At the within-person level, a reciprocal relationship was observed between PSMU and depression over time. Furthermore, SA predicted later increases in PSMU, whereas the reverse associations were not significant. These results highlight the dynamic interplay among emotional symptoms and digital behavior, and underscore the importance of considering both individual differences and temporal fluctuations in future research.