The Conditional Protective Role of Psychological Resilience: School Bullying Climate, Emotional Regulation Difficulties, and Mobile Phone Dependence Among Left-Behind Children

School bullying climate is a known risk factor for adolescent mobile phone dependence, yet the mechanisms linking these two constructs and the boundary conditions of protective factors remain underexplored. The present study aimed to examine the mediating role of emotional regulation difficulties in the relationship between school bullying climate and mobile phone dependence among left-behind children, as well as the moderating role of psychological resilience in this mediating pathway. The final analytical sample consisted of 300 left-behind children who completed two waves of surveys separated by a six-month interval. Participants completed the School Bullying Climate Scale, the Brief Difficulties in Emotion Regulation Scale, the Mobile Phone Dependence Scale, and the Psychological Resilience Scale. Data were analyzed using the PROCESS macro for SPSS (Model 4 for mediation and Model 58 for moderated mediation), controlling for age, gender, and baseline mobile phone dependence. School bullying climate was significantly positively correlated with mobile phone dependence among left-behind children six months later (r = 0.14, p < 0.05), and emotional regulation difficulties mediated this relationship (indirect effect = 0.03, 95% CI = [0.001, 0.077]). Psychological resilience significantly moderated the path from school bullying climate to emotional regulation difficulties (b = 0.19, p < 0.05). Specifically, for left-behind children with high psychological resilience, the relationship between school bullying climate and emotional regulation difficulties was significant (b = 0.29, p < 0.01); for those with low psychological resilience, this relationship was not significant (b = 0.02, p > 0.05). Notably, psychological resilience played a conditional moderating role: only under a low school bullying climate is high psychological resilience associated with lower emotional regulation difficulties in left-behind children.