To analyse the clinical characteristics of children and adolescents with first-episode depression who visited the outpatient clinic, as well as the risk of non-suicidal self-injury (NSSI) and protective factors.

A total of 441 patients with first-episode depression who visited the Child Mental Health Research Centre at Nanjing Brain Hospital affiliated with Nanjing Medical University between January 2020 and December 2023 were selected. Among them, 313 (71.0%) had NSSI and 128 (29.0%) did not. The Children's Self-Awareness Scale and the 90-item Symptom Checklist (SCL-90) were used to assess the clinical symptoms of these children and adolescents. Chi-square tests and independent t-tests were used to compare the differences in clinical characteristics between those with and without NSSI, and Logistic regression was further used to explore the influencing factors.

In the comparison of SCL-90 questionnaire scores, the group without NSSI had significantly lower scores of somatisation (t=-5.342, P＜0.001), obsessive-compulsive symptoms (t=-3.430,P=0.001), interpersonal relationships(t=-5.258, P＜0.001), depression (t=-5.673, P＜0.001), anxiety (t=-4.870, P＜0.001), hostility (t=-5.299, P＜0.001), phobia (t=-3.292, P=0.001), paranoia (t=-5.000, P＜0.001), psychoticism (t=-5.802, P＜0.001), and other (t=-5.854, P＜0.001) than the non-NSSI group. In the comparison of Children's Self-Awareness Scale scores between the two groups, the total self-awareness score (t=3.635, P＜0.001), as well as the scores of self-awareness behaviour (t=4.765, P＜0.001), self-awareness anxiety (t=2.462, P=0.014), and self-awareness happiness and satisfaction (t=3.414, P=0.001), was significantly higher in the non-NSSI group than in the group with NSSI. Further Logistic regression analysis indicated that female gender (odds ratio [OR]=2.033, 95% confidence interval [CI]: 1.188~3.478), somatisation (OR=1.040, 95%CI: 1.005~1.077), interpersonal relationships (OR=1.064, 95%CI: 1.003~1.129), and psychoticism (OR=1.076, 95%CI: 1.019~1.137) were positively associated with NSSI in patients with depression, while horror (OR=0.948, 95%CI: 0.900~0.999), obsessive-compulsive symptoms (OR=0.908, 95%CI: 0.858~0.961), and self-awareness behaviour (OR=0.902, 95%CI: 0.829~0.982) were negatively associated with NSSI.

High-risk factors for NSSI in children and adolescents with first-episode depression include female gender, somatisation symptoms, interpersonal sensitivity, and psychotic symptoms. Protective factors include obsessive-compulsive symptoms, phobic symptoms, and self-conscious behaviour.