Neural Correlates of Non-Suicidal Self-Injury Functions: Neurobiological Vulnerabilities and Psychosocial Risks in Psychiatric Disorders

Non-suicidal self-injury (NSSI) is a common behavior among adolescents, particularly within psychiatric populations. While neurobiological and psychosocial risk factors have been extensively studied, the mechanisms underlying NSSIs heterogeneity remain unclear. This study investigated 304 hospitalized adolescents/young adults (16-25 years) with NSSI and comorbid psychiatric diagnoses (major depressive disorder [MDD], bipolar disorder [BD], eating disorders [ED]) using psychological assessments and resting-state fMRI data from 163 participants. Orthogonal projection non-negative matrix factorization of Ottawa Self-Injury Inventory responses identified two core motivational dimensions: self-related (emotional regulation) and social-related (interpersonal influence). The self-related factor correlated with amygdala-centered cortico-limbic emotional regulation networks and predominated in affective disorders (MDD/BD), while the social-related factor linked to frontoparietal cognitive control and frontotemporal social cognition networks, particularly in ED. Fuzzy C-means clustering revealed three NSSI functional subtypes, independent of diagnostic categories : self-subtype primarily driven by self-related functions, social-subtype influenced by both self- and social-related functions with greater exposure to psychosocial risks, and non-specific subtype with undifferentiated motivations. No subtype was exclusively driven by social-related functions. The "self-social" dual-dimensional neural model demonstrated distinct subtype-specific profiles in functional connectivity, psychosocial risk exposure, and clinical features. Self-related mechanisms primarily engaged emotional regulation circuits, whereas social-related mechanisms emphasize the role of psychosocial risk factors and cognitive-emotional circuits. These findings provide neural evidence for the functional heterogeneity of NSSI and highlight the need for personalized interventions. Treatments targeting emotion regulation may benefit all subtypes, individuals with prominent social-related motivations may additionally require interventions aimed at improving interpersonal functioning.