Introduction: Active travel (walking and cycling) is increasingly being recognised as a potentially effective means of increasing physical activity levels and thereby contribute to physical and mental health. To date, however, much of the empirical evidence related to the health benefits of active travel is based on cross-sectional data. As such, the direction of causation remains uncertain, i.e. does active travel lead to improved health or vice-versa, are healthier individuals more inclined to participate in active travel? This study aims to systematically assess the bidirectional relationships between active travel, on the one hand, and two relevant health outcomes on the other, namely body-mass index (BMI) and mental health. Method: To this end, random-intercept cross-lagged panel models are estimated using data from 10 waves (years) of the Longitudinal Internet Studies for the Social sciences panel, a panel that is representative for the Dutch population. Active travel was assessed using a measure of walking frequency and mental health was measured using the 5-item mental health inventory (MHI-5). Results: The results indicate that active travel does not affect later BMI levels, but, vice versa, BMI does negatively influence later levels of active travel, a pattern that is in line with earlier research related to general physical activity and BMI. Regarding mental health, the pattern is exactly opposite. In this case, the effect of active travel on mental health is significant, while the reverse effect is not (at the 5% level of statistical significance). Conclusion: Overall, the results underline the notion that cross-sectional estimates of the effects between active travel and health outcomes should be interpreted with care, as they can be the result of effects in either direction. In addition, the results suggest that the uptake of active travel may be increased by decreasing BMI levels in the population, e.g. via dietary programs.
- Active travel
- Body-mass index
- Mental health
- Panel data
- Random-intercept cross-lagged panel model