Childhood unpredictability, expressive suppression, and mindfulness as predictors of bystanders' outsider behaviors in cyberbullying among Chinese undergraduates: a moderated mediation model

Background Bystanders' outsider behaviors play a vital role in the development and persistence of cyberbullying incidents, a prevalent form of harmful digital engagement. Prior literature has found an association between childhood unpredictability and bystanders' outsider behaviors in cyberbullying. However, the underlying mechanisms explaining this association remain unclear. To address this, the current study examined the mediating role of expressive suppression and the moderating role of mindfulness between childhood unpredictability and bystanders' outsider behaviors in cyberbullying. Methods A cross-sectional survey was conducted with a total of 1,149 Chinese undergraduates ( M age = 19.48 years, SD age = 2.79, age range: 18–24 years) recruited through a convenience sampling method. Well-validated self-report measures were administered to assess childhood unpredictability, expressive suppression, mindfulness, and bystanders' outsider behaviors in cyberbullying. Structural equation modeling (SEM) was used to test a moderated mediation model in which expressive suppression mediates the association between childhood unpredictability and bystanders' outsider behaviors in cyberbullying, with mindfulness moderating the relationship between expressive suppression and bystanders' outsider behaviors in cyberbullying. Results The study revealed that childhood unpredictability was significantly and positively associated with bystanders' outsider behaviors in cyberbullying among undergraduates. Mediation analysis demonstrated that childhood unpredictability both directly predicted bystanders' outsider behaviors in cyberbullying and indirectly affected them through the mediating role of expressive suppression. Furthermore, the mediating effect of expressive suppression was moderated by mindfulness. Specifically, undergraduates with lower mindfulness showed a stronger association between expressive suppression and bystanders' outsider behaviors in cyberbullying compared to those with higher mindfulness. Conclusion This study enriches existing literature by elucidating that the mediating effect of expressive suppression and the moderating effect of mindfulness represent additional explanations of the association between childhood unpredictability and bystanders' outsider behaviors in cyberbullying among undergraduates. The findings offer empirical evidence for developing targeted interventions aimed at reducing outsider behaviors in cyberbullying and promoting a healthier online environment, thereby contributing to the psychological wellbeing of undergraduates within emerging digital environments.