Double-edged effect of physical activity on non-suicidal self-injury among depressed adolescents: An analysis of underlying mechanisms

Non-suicidal self-injury (NSSI) is an emerging health concern is adolescents. The current research investigated the relationship between physical activity (PA) and NSSI frequency in depressed adolescents and analyzed the mediating role of perceived stress (PS), as well as the moderating role of perceived social support (PSS). 1675 depressed adolescents aged 12 to 18 years across 9 provinces in mainland China were recruited from December 2020 to December 2021. We employed the SPSS PROESS models to test the mediating effects and moderating effects. The age, gender, depression, peer bullying and rumination factors were controlled in the analysis. PA was negatively associated with PS, and PS was positively associated with NSSI frequency. However, PA exerted positive direct impacts on NSSI frequency. The total effect of PA on NSSI was positive and significant. PA exhibits a double-edged effect on NSSI frequency. Notably, for different physical activity levels, the positive impact of PA on NSSI only existed in high PA group. PSS effectively moderated and attenuated the effect of PS on NSSI. An appropriate level of PA should be maintained and the disadvantages of excessive activity should be avoided