The Impact of Upward Social Comparison on Social Networking Sites on Subjective Well-being: A Moderated Mediation Model Involving Appearance Perfectionism, Use Intensity, and Only-child Status

This study explores the underlying mechanisms and boundary conditions of how upward social comparison on social networking sites affects the subjective well-being of college students. Based on the stress-vulnerability-adaptation model, a moderated dual-mediation model was constructed to examine the mediating roles of appearance perfectionism and social networking site use intensity, as well as the moderating role of only-child status. A questionnaire survey was conducted among 389 college students, and data were analyzed using the PROCESS macro in SPSS 26.0. The results indicated that: (1) Upward social comparison positively predicted subjective well-being; (2) Appearance perfectionism and social networking site use intensity fully mediated the relationship between upward social comparison and subjective well-being, with opposite directions, forming a competitive mediation; (3) Only-child status moderated the relationship between upward social comparison and social networking site use intensity—the positive relationship and its transmitted negative mediating pathway were significant only among only-children, while the moderating effect on the appearance perfectionism pathway was not significant. This study reveals the “double-edged sword” effect of upward social comparison on subjective well-being and its differentiated pathways, clarifying the selective moderating role of family structure, thereby providing a basis for targeted online mental health education.