The role of connection with nature in empirical studies with physiological measurements: a systematic literature review.

It is well described that exposure to nature reduces physiological stress, and connectedness to nature can have a moderating effect. However, few studies have so far examined the construction of the connection with nature in relation to physiological processes. In this systematic review, we collected studies that used a physiological measure and included a scale to measure connectedness to nature. Our aim was to assess the role of nature relatedness at the level of physiological processes and to summarize the results published so far. Our review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A literature search was conducted in 3 different databases (PubMed, ScienceDirect and Google Scholar). As keywords, we used all the different questionnaires that measure connectedness to nature, combined with terms related to physiological measures. After final screening, 28 articles met the inclusion criteria for the review. The studies were very diverse in terms of purpose, intervention and methods, so narrative synthesis was conducted without measures of effect. We found evidence for a mediating effect of nature connectedness on the associations between nature exposure and cognitive function, brain activity, blood pressure, cortisol level and mental health. Studies investigating nature relatedness as state-like characteristics have shown that exposure to nature increases the level of connection to nature. Eye-tracking studies have confirmed that this measurement method can be used to investigate nature relatedness at a physiological level, which could be a useful complement to self-report questionnaires in future studies.