Physical exercise and depression in college students: the serial mediating roles of mindfulness and experiential avoidance.

Background: Guided by Acceptance and Commitment Therapy (ACT), this study examined whether trait mindfulness and psychological inflexibility and experiential avoidance-related processes, assessed using the Acceptance and Action Questionnaire-II (AAQ-II), were statistically linked to the association between physical exercise and depressive symptoms among college students.

Methods: A cross-sectional cluster sample was recruited from 11 general physical education classes at one university in Jiangsu Province, China. A total of 308 valid questionnaires were retained from 320 invited students. Participants completed the Physical Activity Rating Scale-3 (PARS-3), Mindful Attention Awareness Scale (MAAS), Acceptance and Action Questionnaire-II (AAQ-II), and Self-Rating Depression Scale (SDS). Data were rechecked for missing values, duplicate records, out-of-range values, and potential outliers. Welchuplt-tests, Pearson correlations, standardized regression path models, and bootstrap-based serial indirect association analyses were conducted in R. Gender was included as a covariate.

Results: The prevalence of at least mild depressive symptoms was 20.78% based on SDS standard scores. Physical exercise was negatively associated with depressive symptoms (β = -0.264, p < 0.001) and positively associated with mindfulness (β = 0.286, p < 0.001). After mindfulness was included, the direct association between physical exercise and AAQ-II-related scores was not significant (β = -0.083, p = 0.113). Mindfulness was negatively associated with AAQ-II-related scores and depressive symptoms, whereas AAQ-II-related scores were positively associated with depressive symptoms. Bootstrap analyses showed a significant indirect association through mindfulness and a significant serial indirect association through mindfulness followed by AAQ-II-related scores. The indirect path through AAQ-II-related scores alone was not significant.

Conclusion: Physical exercise was associated with lower depressive symptoms among college students, and this association was statistically linked to trait mindfulness and AAQ-II-related scores in a serial pattern. AAQ-II-related scores did not operate as an independent indirect pathway but appeared mainly within the pathway following mindfulness. Because the study was cross-sectional and based on self-report data from a single university, the findings should be interpreted as cross-sectional indirect associations rather than evidence of causal mediation.