Time in nature is associated with higher levels of positive mood: Evidence from the 2023 NatureDose™ student survey

Abstract

Growing evidence shows that exposure to nature can improve mood. However, this evidence is mostly based on short-term or subjectively reported exposures. Machine learning and GPS mobile device tracking offer fine-grained assessments of minute-by-minute nature exposure over long periods. Few studies on nature exposure and mood have leveraged these technologies. We conducted one of the first longer-term investigations of daily nature exposure and mood with a mobile app as part of the NatureDose™ Student Study (NDSS). The NatureDose™ app uses GPS and a phone's sensors to evaluate whether a person is inside or outside and checks levels of nature surrounding the person with the NatureScore™ measure. This measure is based on more than 30 remotely sensed datasets, geo-located health records, and machine learning models. College students' nature exposure (N = 154 initial recruitment) was monitored for eight weeks (March 7 to May 1, 2022). Their mood states were calculated weekly using the Positive and Negative Affect Schedule (PANAS). Both exposure and outcome measures were continuous values. After three weeks, randomly selected groups of students were asked to either maintain or increase their nature exposures. However, students asked to increase their nature exposures maintained them. Therefore, evaluating cause-and-effect relationships through an experimental design was not possible. Instead, we evaluated observational associations between average nature exposure and mood levels across the study period using mixed-effect linear regression models adjusting for gender and allergies. Among the 97 participants with available data, we observed a positive association between nature exposure and positive mood (β = 0.10 [0.04–0.17], p = .003) but not negative mood (β = 0.01 [-0.07-0.09], p = .76). These findings were supported by sensitivity analyses with ANOVA models between tertiles on average NatureDose™ levels. We also found that the average nature exposure was 71 min per day, most of which (66%) was earned within 10 km of the center of the university campus. The study supports the utility of using NatureDose™ as an app-based tracking tool for objective nature exposure measurement. The study also reinforces previous findings on the associations between nature exposure and positive mood states. Greening university campuses and surrounding locations where college students live and spend leisure time could support college students' mental health.