Biological Underpinnings of Non-Suicidal Self-Injury in Adolescence: A Narrative Review

Non-suicidal self-injury is a significant adolescent mental health problem and a risk factor for suicide. Understanding the biological mechanisms of self-injurious behavior is crucial for developing effective diagnostic and therapeutic strategies. Aim: To summarize and critically analyze contemporary scientific data on the biology of non-suicidal self-injury in adolescents. Methods. A narrative review was conducted (databases searched: MEDLINE, Web of Science, eLIBRARY.RU, CyberLeninka). Studies investigating biological aspects of non-suicidal self-injury in adolescent samples were included. Findings from selected studies were structured according to biological systems, and data were synthesized with regards to the interplay between these systems within the developmental trajectory of self-injurious behavior. Results. The review revealed multisystem impairments in non-suicidal self-injury: structural and functional brain changes (particularly in the prefrontal cortex, somatosensory areas, and default mode network); dysfunction of neurochemical systems (deficit in endogenous opioids, alterations in endocannabinoids); dysregulation of both hypothalamic-pituitary-adrenal axis and autonomic nervous system (hyporeactivity to psychosocial stress, hyperreactivity to pain); activation of immune-inflammatory mechanisms; reduced pain sensitivity; and genetic (moderate heritability, serotonin-related gene polymorphisms) and epigenetic factors (hypermethylation of POMC ). Complex interplay between biological factors within a temporal framework (distal predictors, proximal correlates, immediate episode-related factors) is discussed. Conclusion. Non-suicidal self-injurious behavior in adolescents is characterized by multisystem biological dysfunctions shaped by genetic predisposition and environmental factors. Despite data heterogeneity, the findings deepen our understanding of the mechanisms underlying the development and progression of non-suicidal self-injury and open prospects for developing risk biomarkers and biologically informed, personalized therapeutic approaches. Longitudinal studies integrating the assessment of biological and psychosocial factors are necessary to overcome current methodological limitations.