Intensity-specific leisure-time physical activity and depressive symptoms among first-year university students: a four-wave longitudinal study

Background Depressive symptoms are common among first-year university students, yet the longitudinal associations between different intensities of leisure-time physical activity (LTPA) and mental health remain unclear. This study examined the relationships between moderate- and vigorous-intensity LTPA and depressive symptoms over one academic year, as well as potential gender differences. Methods A four-wave longitudinal survey was conducted over one academic year among 456 freshmen (Mage = 18.18, SD = 0.67; 202 males and 254 females). Latent growth modeling was employed to analyze temporal changes in depressive symptoms and LTPA, and a parallel process latent growth model was used to assess the relationships between LTPA intensity and depressive symptom trajectories. Results Depressive symptoms were relatively elevated at the beginning of the academic year and showed a modest decline over time, whereas LTPA increased across waves. The intercepts of vigorous-intensity LTPA and depressive symptoms were significantly and negatively associated ( β = − 0.441, p = 0.002), whereas the association between moderate-intensity LTPA and depressive symptoms at baseline was not statistically significant ( β = − 0.278, p = 0.071). Importantly, no significant associations were observed between changes in LTPA and changes in depressive symptoms over time (moderate: β = − 0.187, p = 0.508; vigorous: β = − 0.061, p = 0.823). Female students reported lower baseline levels of both moderate- and vigorous-intensity LTPA compared with males; however, no significant gender differences were observed in the longitudinal associations between LTPA and depressive symptoms. Conclusions Vigorous-intensity LTPA and depressive symptoms were negatively associated at baseline among first-year university students. However, changes in LTPA were not significantly related to changes in depressive symptoms over the study period. These findings underscore the importance of distinguishing between baseline associations and longitudinal change when interpreting relationships between physical activity and mental health.