Are actual and perceived environmental conditions associated with variation in mental health?

Empirical evidence on the relationship between environmental factors and mental health remains inconclusive. One reason is that there is only scant evidence on the association between mental health and subjective exposure to environmental stressors, relative to objective pollution. We thus focus on how the perceived and actual presence of noise, air pollution, and green spaces relates to mental health. Our cross-sectional study is based on a large representative sample of the adult population in Switzerland (n = 5729). Using individual-level geocodes of subjects' residence, we combined data from a survey of these individuals with data on objectively measured longer-term environmental conditions (noise, air pollution, green spaces). Subclinical mental health was assessed with the 12-item General Health Questionnaire (GHQ-12). When fitting multiple regressions and mediation models, we find that perceptions of environmental stressors are a better predictor of mental distress than objectively measured stressors. In addition, the predictive power of actual nature visits is stronger than the predictive power of mere proximity to green spaces at the place of residence. We found no direct link between actual environmental stressors and mental health, but mediation via perceived environmental stressors. Further, the association between the frequency of nature visits and mental health is mediated by perceived, but not actual pollution. Since actual environmental stressors are not perceived as equally burdensome by all people, their subjective perception is crucial when evaluating policy interventions aimed at improving mental health. Even a relatively low level of environmental stressors, classified as non-harmful to human health in a physical or biological sense, may thus contribute to negative mental health outcomes. The main policy implication is that attractive and accessible green spaces may provide individuals with an enhanced sense of control over their exposure to environmental stressors and thereby reduce negative impacts.