Mechanisms and Heterogeneous Effects of Physical Activity on Mental Health: Evidence from the China Family Panel Studies

Objectives: In recent years, mental health has emerged as a pressing public health concern in China, driven by mounting societal pressures and fast-paced urban lifestyles. Physical activity, a well-established means of enhancing psychological well-being, has received growing scholarly and policy attention. This study uses panel data from the 2020 and 2022 waves of the China Family Panel Studies (CFPS) to examine the impact of exercise frequency on mental health (with indicators such as CESD-8 depression scores) among college students and young employees, thereby providing empirical support for targeted mental health interventions. Methods: This study examines the relationship between individual exercise frequency and mental health among college students and young employees, using panel data from the 2020 and 2022 waves of the China Family Panel Studies (CFPS), with the Chinese version of the 8-item Center for Epidemiologic Studies Depression Scale (CESD-8) depression scores, self-rated health, and life satisfaction as outcome variables. Specifically, this study tests three hypotheses: (H1) increased exercise frequency significantly reduces depression symptoms and enhances well-being; (H2) the effects of exercise vary by social roles, with stronger mental health benefits among employed individuals and those with lower education; and (H3) lifestyle factors such as smoking amount, sleep duration, and Body Mass Index (BMI) partially mediate the relationship between exercise and mental health. Employing a two-way fixed effects model, baseline results indicate that a one-unit increase in exercise frequency significantly reduces the CESD-8 score by 0.183 points. To address potential endogeneity and spurious regression concerns, an instrumental variable (IV) approach is further applied. The heterogeneity analysis differentiates between students and employed individuals. Results: Among students, the effects of exercise on mental health are not statistically significant, regardless of education level. In contrast, for the employed, exercise demonstrates a significant positive impact on mental health, with particularly pronounced effects among those with lower educational attainment. These findings underscore the importance of promoting exercise as part of comprehensive mental health strategies. Mediation analysis indicates that the beneficial effect of exercise on mental health is partially transmitted through reductions in adverse health behaviors, especially smoking. Conclusions: Policymakers should integrate physical activity promotion into health interventions, prioritizing vulnerable groups to enhance psychological resilience and foster inclusive, health-oriented development.