Associations between 24-hour movement behavior and non-suicidal self-injury in adolescents: based on compositional...

Evidence suggests that physical activity (PA) is closely associated with lower non-suicidal self-injury (NSSI). However, the relationship between 24-h movement behaviors and NSSI, as well as potential substitution effects among these behaviors, remains unclear. Therefore, this study investigates how relative time allocation across movement behaviors and the substitution effects between them relate to NSSI.

A total of 536 adolescents wore the ActiGraph wGT3X-BT triaxial accelerometer for 7 consecutive days to measure moderate-to-vigorous physical activity (MVPA), light-intensity physical activity (LPA), and sedentary behavior (SB); sleep duration was assessed via sleep diaries. NSSI scores were measured using the Self-Injury Behavior Scale (SIBS). Data were analyzed using compositional data analysis and the isotemporal substitution model.

Compositional regression showed a negative association between MVPA and NSSI scores and a positive association with SB. Isotemporal substitution using 15-minute increments indicated that replacing LPA and SB with MVPA was associated with reductions in NSSI scores of 0.31 and 0.37 units. Replacing SB with sleep was associated with a decrease in NSSI scores of 0.18 units. A significant interaction between sleep proportion and gender was observed, indicating sex-specific associations. Dose-response analysis further showed that substituting SB with MVPA produced the greatest reduction in NSSI, with effects attenuating after 20 min.

Within the 24-h movement behavior framework, reallocating some SB time to MVPA may help reduce NSSI among adolescents. This finding improves our understanding of activity-related mechanisms in NSSI and informs targeted interventions.