David Yaden of the School of Arts & Sciences says, “There have been studies comparing walking in nature with walking in an urban environment and testing people on their mood, different aspects of depression and in some cases, brain scans.”
https://www.washingtonpost.com/news/to-your-health/wp/2016/05/17/forest-bathing-is-latest-fitness-trend-to-hit-u-s-where-yoga-was-30-years-ago/?tid=pm_national_pop_b The Washington Post