In hospital recovery rooms, recovering surgery patients with window views looking out upon trees had 10% shorter hospital stays, took fewer potent pain killers during their recovery, and had fewer negative notes recorded by their attending nurses than patients with views looking out at a brick wall.
Ulrich, Roger. “View through a Window May Influence Recovery from Surgery.” Science 224, no. 4647 (1984): 224–225. https://doi.org/10.1126/science.6143402.