Twenty-five adults each spent 90 minutes in a forest and, on a separate day, 90 minutes in an industrial environment, then cycled to exhaustion in a laboratory. Daniel Longman ran it in randomised, counterbalanced order in 2026. After the forest they lasted 14.6 minutes. After the industrial exposure, 13.5 minutes, at p = 0.007. Mood was worse after the industrial exposure and people stopped at a lower perceived exertion, while the cardiorespiratory readings taken during the test did not differ.
In 2023 Ziquan Liu pooled the observational literature onto a common footing. Ten per cent more green space in an area went with an odds ratio of 0.963 for depression and anxiety, with a confidence interval of 0.948 to 0.979. A 0.1 unit rise in the normalised vegetation index went with 0.931 for depression.
Wenzhen Li asked 1,380 non-healthcare workers in Hong Kong about the greenery near their home and their workplace between March 2023 and December 2024, splitting it into abundance, visibility, access and use. Perceived access tracked the mental component of quality of life at β = 0.54 and lowered the odds of anxiety and of depression to 0.93 each. Visibility tracked the physical component at β = 0.41. Li’s conclusion is about planning: how reachable the greenery feels matters alongside how much of it there is.
Yannick Klein used the Swedish occupational health survey to look at the same question through the pandemic, with 984 respondents. Loneliness rose most among those working remotely most of the time. Daily visits to nature went with lower loneliness, and most clearly in that group, as a three-way interaction between remote work, nature habits and time.
Juhye Kweon ran a forest healing programme with 62 people in 2024: 20 healthcare providers, 21 IT specialists and 21 teachers. Sleep, depression scores and stress all improved. Morning salivary cortisol fell significantly, while the rise in melatonin and the fall in DHEA-S did not. The teachers took part during school holidays and showed almost no physiological change.
Only Longman randomised anything. Liu pools observational work, Li and Klein report surveys, and Kweon measured before and after with no control group.