As far as we know, this study breaks new ground by using machine learning and SHAP explainability methods to analyze the risk factors of SA in adolescents with depression, using a large, nationally representative sample. Furthermore, it explores how these risk factors interact through a moderated mediation model. The findings undescore the prominence of emotion-focused coping, rumination, and school bullying as robust and top determinants of SA, consistently observed among 35 risk factors across diverse models. Notably, through subsequent mediation moderation analysis grounded in the I-PACE model, it is revealed that rumination serves as a significant mediator in the relationship between school bullying and SA, while emotion-focused coping significantly moderates the relationships between school bullying and both rumination and SA. This amalgamation of data-driven approaches and theoretical models not only advances our understanding of SA predictors but also provides a framework for targeted intervention strategies for depressed adolescents.
In recent years, machine learning has garnered increasing attention from researchers due to its ability to identify complex nonlinear relationships between variables and its powerful high-dimensional data processing capabilities. However, traditional machine learning methods cannot provide the contribution of each factor to the prediction outcome. The advent of the SHAP method has addressed this shortcoming. This is the first study to combine machine learning with the SHAP method to investigate the predictive factors of SA in adolescents with depression. SA is influenced by numerous factors, and previous studies have struggled to comprehensively include relevant variables. Guided by the I-PACE model, this study has endeavored to collect as many predisposing factors, mediating factors, moderating factors, and relevant demographic variables as possible. Ultimately, the results from three machine learning models—random forest, logistic regression, and decision tree—consistently indicate that emotion-focused coping, rumination, and school bullying are significant predictive factors for SA in adolescents with depression.
Consistent with previous studies (Vessey et al., 2022; Chen et al., 2021; Kim, 2021), this study found that school bullying significantly predicted SA. Among Chinese middle school students, the prevalence of bullying is between 1.68% and 10.60%, and the victimization rate ranges from 5.91–25.70% (Peng et al., 2019). Individuals who suffer from school bullying are often ostracized by their peers as well, prompting them to hate group life even more (Copeland et al., 2013), which makes them withdrawn and prone to SA. According to the Internet compensation theory, when experiencing psychosocial problems, individuals may use the Internet or smartphones to escape real life issues and relieve negative emotions (Kardefelt-Winther, 2014). Apparently, such a strategy led to poorer well-being and behavioral problems, like SA (Weidman et al., 2012). Previous studies have only explored the direct impact of bullying in schools on SA, while this study further focuses on other factors that may influence this pathway.
For the first time, we found the mediating role of rumination between school bullying and SA in adolescent depression. This means that the effect of school bullying on SA was predicted on one hand through the direct effect of school bullying and on the other hand through the mediating role of rumination. Consistent with the results of previous research, school bullying triggers individuals to rumination. Then to cope with the negative emotions associated with rumination, they overuse smartphones (Zou et al., 2023; Peng et al., 2022). According to the cognitive-behavioral model of pathological Internet use (Davis, 2001), although SA is a result of negative life events such as school bullying, maladaptive cognitions about the self, namely rumination, is the most central factor causing SA directly.
Emotion-focused coping is the most important predictor of SA in adolescents with depression found in our study, across all machine learning models, while problem -focused coping does not predict SA. In depressive patients, emotion-focused coping can lead to increased SA due to its nature of providing immediate emotional relief but failing to address underlying issues. Emotion-focused coping strategies, particularly those involving avoidance, may reinforce negative behavior patterns and worsen depressive symptoms, creating a feedback loop that increases SA. Problem-focused coping, while potentially less immediately gratifying, aims to tackle the root causes of stress and depression, offering long-term benefits and reducing the need for smartphones as a coping mechanism.
The present study found that both the effects of school bullying on SA and school bullying on rumination were moderated by emotion-focused coping in adolescents with depression. The effects of school bullying on both SA and rumination were stronger in depressed adolescents with lower levels of emotion-focused coping compared to those with higher levels of emotion-focused coping (Stanton et al., 1994; Stanton and Low, 2012). Emotion-focused coping may provide immediate, albeit temporary, relief from depressive symptoms through smartphone use. Therefore, for depressed adolescents with lower levels of emotion-focused coping, due to the lack of effective coping methods, the negative cognition brought about by school bullying, namely rumination, and behavioral problems, namely SA, may be more intense. However, in the long run, individuals with higher levels of emotion-focused coping have higher levels of rumination and SA brought about by school bullying than those with lower levels of emotion-focused coping. The method of emotion-focused coping is still a risk factor for SA in adolescent patients with depression.
In conclusion, we use machine learning to explore the predictors of SA in depressed adolescents and to analyze the interactions between important predictors. These findings have important implications for reducing SA in adolescents with depression, especially those school bullying victims. In future clinical work, we can intervene in SA from two perspectives: emotion-directed coping and rumination. First, we guide patients to reduce the use of emotion-directed coping in favor of problem-oriented coping. Second, rumination-focused cognitive behavior therapy, cognitive bias modification, and cognitive control training can be used to reduce rumination (Watkins and Roberts, 2020).