Natural environments and chronic stress measured by hair cortisol

Neighbourhood green space is positively associated with health. Stress reducing effects of nature might underpin this relationship, but researchers have often used objective stress measures to characterise acute responses to natural environments, or used self-reported measures in observational research. Hair cortisol concentration (HCC) is a novel non-invasive biomarker, with potential to improve our understanding of natural environments and chronic stress. We collected data from 132 healthy employed adults from the West Midlands region of the UK (June –Sept 2014), including socio-demographics, health, lifestyle and perceived stress and stress appraisal. Postcode was used to determine overall deprivation (Index of Multiple Deprivation, IMD), material deprivation (% income deprived) and the amount of natural environment in participants’ home neighbourhoods. Hair samples (3cm) were taken from the scalp and HCC was determined to reflect past three months of cortisol secretion. Separate linear regression models, adjusting for potential confounders, indicated that HCC-measured chronic stress was higher in participants who lived in areas that were more deprived overall (β=-.235, p=.008), more income deprived (β=-219, p=.017), and comprised less natural environment (β=-212, p=.019). When income deprivation (i.e., material well-being) and natural environment were entered in the same model, associations for both were attenuated beyond significance (β=.168, p=.077 and β=-.160, p=.086, respectively). Overall, chronic stress measured by HCC was higher in areas with less natural environment. The relative contribution of neighbourhood natural environment, deprivation and other neighbourhood characteristics to chronic stress using HCC warrants further study in larger, more diverse samples.