Impulsivity, time perception and non-suicidal self-injury in adolescents: from behavioral and fNIRS evidence

Background: Elevated impulsivity and temporal processing deficits are key risk factors for adolescent non-suicidal self-injury (NSSI); however, their joint neural substrates and specific contributions to NSSI remain inadequately characterized. This study aimed to elucidate the behavioral and neural interplay between these cognitive domains in adolescents with NSSI. Methods: We recruited 44 adolescents with NSSI and 37 typically developing (TD) controls. Participants completed the Barratt Impulsiveness Scale (BIS-11), a Choice Delay Task (CDT), and time perception assessments (discrimination and estimation tasks). A subsample (33 NSSI, 30 TD) subsequently underwent functional near-infrared spectroscopy (fNIRS) to monitor prefrontal hemodynamic responses during an oddball task, a paradigm assessing inhibitory control. Results: Compared to TD controls, adolescents with NSSI exhibited significantly elevated trait impulsivity (BIS-11), heightened delay aversion (preference for immediate rewards in CDT), impaired short-interval temporal discrimination (600ms), and a consistent underestimation of time intervals (7s, 12s, 34s, and 90s). Stepwise regression analysis identified BIS-11 scores, 600ms discrimination thresholds, and 90s estimation bias as significant predictors of NSSI. Neuroimaging revealed that the NSSI group showed lower accuracy on the oddball task and significant hypoactivation in the left dorsolateral prefrontal cortex (L-DLPFC). Crucially, reduced L-DLPFC activation was associated with greater time estimation errors (at 12s and 34s) and increased NSSI. Conclusion: Adolescents with NSSI display a distinct neurocognitive phenotype characterized by high impulsivity and distorted time perception. These deficits may be associated with reduced activation in the L-DLPFC. Our findings suggest that NSSI involves a dual failure of inhibitory control and temporal processing, indicating that interventions targeting prefrontal regulation may offer novel strategies for risk reduction.