The effect of physical activity on depression: a lagged mediation study of school burnout
Authors: Ye ZIcong , Peng Ying , Rao Wei , Zhang Ting 
Published: January 2024

Purpose
In recent years, the problem of suicide among college students has become increasingly serious, and depression has become the root cause of this problem, which has attracted extensive attention from many colleges and universities at home and abroad. At present, medication is the main means to control depression, but it is not infallible and has certain side effects. Therefore, based on the burnout theory, this paper explores in depth the intrinsic connection between the amount of physical activity, depression and academic burnout. We explored the cross-sectional relationship between physical activity level, depression and academic burnout at two separate time points through two questionnaires in one semester. In order to further clarify whether the mediation effect has a lagged effect in this model, we built two lagged mediation models to explore the amount of mediation effect. Also, we developed parallel mediation models to explore which mediation effect was more significant between physical activity and depression. In addition, we quantitatively graded physical activities to explore which physical activities had the best effect on improving academic burnout and depression among college students.
Methods
We conducted a longitudinal study utilizing the physical education classroom. Using questionnaires, students' physical activity, school burnout, and depression were measured twice during one semester. The first test was administered shortly after the start of the first semester of the 2023 school year (Time 1) and the second test was administered before the final exams of the first semester (Time 2). A Total of 305 valid participants were obtained for the first test and 305 for the second test. SPSS 27.0 was used as the data processing tool and detailed descriptive statistics and correlation analyses were conducted to determine the relationship between the variables at each point in time. We then used multiple linear regression to explore the mediating relationships between the amount of physical activity, school burnout, and depression across cross-sections and attempted to explore whether there was a lagged effect of physical activity on school burnout and depression. Finally, we graded the amount of physical activity to explore which intensity of physical activity best influenced school burnout and depression.
Results
In the first cross-sectional study, school burnout (Time 1) would serve as a mediator between physical activity (Time 1) and depression (Time 1) among college students (effect value of -0.002, bootCI range from − 0.004 to -0.002 ).In the second cross-sectional study, school burnout (Time 2) would be a mediator between physical activity (Time 2) and depression (Time 2) among college students (effect value of -0.004, bootCI range from − 0.005 to -0.0002 ). Further testing for lagged mediating effects, school burnout (Time 1) would be a mediator between college students' physical activity (Time 1) and depression (Time 2) (effect value of -0.002, bootCI range from − 0.003 to -0.001 ). School burnout (Time 2) will be a mediator between college students' physical activity (Time 1) and depression (Time 2) (effect value of -0.002, bootCI range from − 0.003 to -0.001 ). Finally, we compared the lagged mediating effects of the two groups and found that the effect of school burnout (Time 2) as a mediator was more significant (effect value of -0.002, bootCI range from − 0.003 to -0.001 ).After finding that school burnout (Time 2) had the most significant effect on physical activity and depression, we graded the amount of physical activity according to the scale and found that only high-intensity physical activity affected depression(Time 2) through school burnout(Time 2) (effect value of -0.277, bootCI range from − 0.406 to -0.158 ).
Conclusion
There is temporal stability between physical activity, depression, and school burnout among college students. That is, school burnout fully mediates the relationship between physical activity and depression at various time points in the cross-section. School burnout acts as a full lag mediator between physical activity and depression. School burnout (Time 2) mediated between physical activity (Time 1) and depression (Time 2) at different intensities to a greater extent than school burnout (Time 1). After quantitative grading of physical activity, the study found that high-intensity physical activity was more effective in reducing symptoms of depression and school burnout.