2006, Psychological effects of forest environments on healthy adults: Shinrin-yoku (forest-air bathing, walking) as a possible method of stress reduction

Morita E, Fukuda S, Nagano J, Hamajima N, Yamamoto H, Iwai Y, Nakashima T, Ohira H, Shirakawa T

Public Health. 2007 Jan;121(1):54-63. Epub 2006 Oct 20

https://www.ncbi.nlm.nih.gov/pubmed/17055544