# Does cycle commuting reduce the risk of mental ill-health? An instrumental variable analysis using distance to nearest cycle path

## TL;DR

This study finds that cycle commuting is linked to a lower risk of mental ill-health, using data from Edinburgh and Glasgow.

## Contribution

The study uses an instrumental variable approach with administrative data to establish a causal link between cycle commuting and mental health.

## Key findings

- Cycle commuters had a 15.1% lower rate of mental health prescriptions compared to non-cyclists.
- The study used road distance to cycle paths as an instrumental variable to reduce bias.
- Findings support promoting cycling as a means to improve mental health.

## Abstract

Previous studies have linked cycling with improved mental wellbeing but these studies tend to use cross-sectional survey data that have small sample sizes and self-reported health measures, and are potentially susceptible to omitted-variable bias and reverse causation. We use an instrumental variable approach and an objective measure of mental ill-health taken from linked administrative data to ask: ‘Does cycle commuting reduce the risk of mental ill-health?’

Our study links data on commuting in Edinburgh and Glasgow from the Scottish population census with mental health prescriptions from the National Health Service Prescribing Information System records. We use road distance from home to nearest cycle path as an instrumental variable for cycle commuting.

In total, 378 253 people aged 16–74 years living and working in the City of Edinburgh and Glasgow City council areas at the 2011 census were included in our study; 1.85% of commuters in Glasgow and 4.8% of commuters in Edinburgh cycled to work. Amongst cyclists, 9% had a prescription for mental health compared with 14% amongst non-cyclists. Using a bivariate probit model, we estimate a mean average reduction in prescriptions for antidepressants and/or anxiolytics in the 5 years following the census of –15.1% (95% CI: –15.3% to –15.0%) amongst cycle commuters compared with those who use any other mode to commute.

This work suggests that cycle commuting is causally related to reduced mental ill-health and provides further evidence in support of the promotion of active travel to encourage commuters travelling shorter distances to shift to cycle commutes.