Longitudinal changes in MMN and P3 during emotional processing in adolescents who engage in NSSI: a 12-week follow-up study.

Background: Adolescents with nonsuicidal self-injury (NSSI) often show deficits in negative emotion regulation. Within the dual-process framework of implicit and explicit emotion regulation, these deficits may reflect an automatic bias toward negative information and insufficient later-stage controlled regulation. Whether routine clinical intervention modifies both early automatic detection and later controlled evaluation of negative emotional information remains unclear. Methods: In a longitudinal sample of 32 adolescents with NSSI, we examined changes in mismatch negativity (MMN) and P3 components elicited during an emotional oddball task before and after a 12-week clinical intervention. At baseline and Week 12, participants completed clinical assessments and a two-choice visual emotional oddball task containing neutral standards and negative, positive, and neutral deviants while EEG was recorded. MMN (Fz, 240-300 ms) and P3 (Pz, 450-650 ms) amplitudes were derived from deviant-minus-standard difference waves, indexing pre-attentive deviance detection and controlled evaluation, respectively. Results: The intervention selectively modulated neurocognitive processing of negative deviants. Self-injury ideation days ( Conclusions: A 12-week intervention may attenuate automatic negative bias while enhancing controlled evaluative processing in adolescents with NSSI, consistent with the implicit-explicit framework. MMN and P3 may serve as candidate biomarkers and temporally sensitive tools for tracking intervention response when behavioural performance is stable.