Personality traits and propensity for self-injurious behaviours in adolescents with and without major depressive disorder: a case-control study

Abstract Background Non-Suicidal Self-injury is a critical public health concern among adolescents, often co-occurring with depression and associated with severe psychopathology. Despite its clinical relevance, research in Middle Eastern contexts remains limited. This study examined the methods, correlates, and mechanisms of self-injurious behaviours among Egyptian adolescents with and without major depressive disorder (MDD). Methods A case–control observational study recruited 110 adolescents (55 with MDD and 55 matched controls) from the Child and Adolescent Psychiatry Outpatient Clinic, Suez Canal University, Egypt. Diagnoses were established using DSM-IV-TR criteria. NSSI was assessed with the Deliberate Self-Harm Inventory (DSHI), and personality traits with the Junior Eysenck Personality Questionnaire (JEPQ). Between-group comparisons used chi-square and t-tests; associations were evaluated with Spearman’s correlations. Mediation was tested with structural equation modeling. Results NSSI was significantly more prevalent among adolescents with MDD (89.1%) than controls (56.4%, p < 0.001). The MDD group reported a greater variety of NSSI methods (mean 4.49 ± 3.98 vs. 2.11 ± 2.57, p < 0.001), with cutting the most common form. Recurrent NSSI and recent episodes (within 6 months and past year) were also more common in the MDD group. Neuroticism scores were significantly higher in the MDD group and showed positive correlations with the number of NSSI methods and frequency in both groups. Mediation analysis further indicated that depressive symptoms partially mediated the relationship between neuroticism and last-year NSSI frequency when adjusting for age and sex. Conclusion Adolescents with depression demonstrate higher rates, greater severity, and more diverse patterns of NSSI compared to healthy peers. Neuroticism emerged as a central personality factor linked to NSSI directly and indirectly through depressive symptoms. These findings underscore the importance of routine NSSI screening in clinical practice and the development of culturally sensitive interventions targeting emotional vulnerability among Egyptian youth.