Quantifying the importance of factors in predicting non-suicidal self-injury among depressive Chinese adolescents: A comparative study between only child and non-only child groups

Background: Depression is a major global public health concern, often co-occurring with Non-Suicidal Self-Injury (NSSI). Focused on Depressive adolescents, this study aimed to quantify the importance of factors in predicting NSSI and compare them between the only child and non-only child groups, enriching knowledge to leverage tailored intervention strategies. Methods: A large multicenter survey was conducted in China. 2510 adolescents diagnosed with Major Depressive Disorder (MDD) volunteered for the study. 36 factors were included to train random forest models for NSSI prediction in only child and non-only child groups, respectively. The SHapley Additive exPlanations (SHAP) method was utilized to compute the relative importance of each factor in two groups. Results: Adolescents with MDD exhibited a rather high prevalence of NSSI (52.0 %), among them 66.9 % were non-only children. Self-esteem was the most significant factor for both groups, while critical disparities of factors were also found. In the only child group, factors like family support, parental overprotection, drinking alcohol, sleep conditions and romantic relationship involvement showed greater importance, while higher depression degree, anxiety level and emotional abuse were more important factors for non-only children. Limitations: The use of cross-sectional data from Chinese adolescents may limit deeper analysis of NSSI mechanisms and the generalizability to Western cultures. Conclusions: Only and non-only child family structures may have different influence on factors related with NSSI occurrence of adolescents with MDD. Only children were more susceptible to vulnerable family environments, alcohol abuse and romantic experience, while non-only children were more disturbed by abnormal mental states.