The relationship between exercise habits and mental health among university students in China: a cross-sectional study based on instrumental variable analysis

Background Exercise habits significantly influence the mental health of university students. However, previous research has often neglected the endogeneity issues in this context, leading to biased estimates and limiting the ability to establish a clear causal relationship. This study aimed to address endogeneity issues and investigate the causal effect of exercise habits on the mental health of university students. Methods This cross-sectional study was conducted involving 1,120 university students from China. Data on demographic characteristics, exercise habits, and mental health were collected using both online and offline questionnaires. To evaluate the mental health benefits of exercise habits, we employed both the instrumental variable (IV) approach and ordinary least squares (OLS) regression. Results The OLS estimates revealed a positive association between exercise habits and positive affect (beta = 0.179, p < .001), life satisfaction (beta = 0.134, p < .001), and self-actualization (beta = 0.086, p < .001) among university students. The IV analysis indicated that exercise habits positively influenced positive affect (beta = 0.263, p < .001), life satisfaction (beta = 0.151, p = .006 < .01), and self-actualization (beta = 0.102, p = .013 < .05). A comparison of the estimation results suggests that the OLS approach underestimates the mental health benefits of exercise habits. Conclusions This study provides preliminary causal evidence that exercise habits contribute to the promotion of mental health in university students. These findings offer valuable insights into potential preventive strategies for addressing mental health issues in this population through exercise interventions.