A comparison of identity development and mindfulness levels between adolescents with and without non-suicidal self-injury

Introduction Non-suicidal self-injury (NSSI) is common but poorly understood in adolescence, and the relative contributions of identity development, mindfulness, family functioning, and comorbid depression to its occurrence remain unclear. Methods In this cross-sectional study we compared these four dimensions in 118 adolescents aged 12–18 years recruited at a tertiary university hospital in Türkiye, in three groups: 41 with NSSI, 40 psychiatric controls, and 37 non-psychiatric outpatient controls. Participants underwent a semi-structured diagnostic interview and completed measures of identity development, mindfulness, and family functioning. Results Adolescents who engaged in NSSI showed greater identity confusion and lower mindfulness than either control group, and identity confusion was linked to lower scores across all mindfulness facets. The NSSI group was also older, predominantly female, and had a substantially higher rate of depression than the psychiatric control group (63.4% vs. 25.0%). In a logistic regression model adjusted for age and sex, a current diagnosis of depression was associated with markedly higher odds of NSSI (adjusted odds ratio 6.5, 95% confidence interval 2.4–17.9), as was identity confusion (adjusted odds ratio 3.5, 95% confidence interval 1.3–9.3), although the estimate for identity confusion was attenuated when overall mindfulness was added. In an exploratory model of the mindfulness facets, higher non-reactivity to inner experience showed a weak inverse association with NSSI (odds ratio 0.90, 95% confidence interval 0.81–0.997), which we regard as hypothesis-generating. Conclusion Identity confusion and low mindfulness most clearly distinguished adolescents who engaged in NSSI from both control groups. The findings identify identity development and mindfulness, alongside depression and family functioning, as candidate targets for clinical assessment and future intervention research in adolescent NSSI, although the cross-sectional design precludes causal inference.