A recent study found that there is convincing evidence that time in nature reduces depressive symptoms, decreases stress and improves cognitive function. More time in the green is associated with lower blood pressure, strengthened immune systems, alleviated risk of heart discase and improved sleep.
In a 2024 study, Maddock and his colleagues looked at outpatient mental health service usage, mostly for depression, anxiety or stress, across 1,169 zip codes in Texas. They found that rates of mental health service use were about 50 percent lower in neighborhoods with more greenery. In 2022 Jimenez and her colleagues published a paper in JAMA Open Network using data from the long-running Nurses' Health Study II to show that living in areas with more green space was associated with higher scores for overall cognition and for psychomotor speed and attention. This difference could be partly explained by fewer depressive symptoms.
There are several possible explanations for these findings. One theory holds that nature provides a short break from the mental fatigue of modern life and the built environment, thereby restoring attentional resources. A 2024 experiment that had nearly 100 participants offers support for the idea: the researchers found that a 40-minute walk in nature enhanced people's ability to adjust higher-level cognitive functions——such as problem-solving and multitasking——more than a40-minute walk in an urban environment did.
A second theory suggests that time spent in nature activates the parasympathetic(副交感的)nervous system, which reduces the body's stress responses. Studies show reductions in cortisol(皮质醇) levels—part of those responses—after exposure to greenery. In addition, green space affects health indirectly because time outdoors encourages physical activity and offers chances for social connection, both of which improve mental and physical well-being.
Studies such as Jimenez's and Maddock's are aimed at policymakers more than individuals, but they remind us all of the importance of seeking out greenery wherever we live. And we should all try to heed the advice that Jimenez gives to her students: "I see how stressed they are, especially during exams," she says. "I tell them, 'Go out for a walk.'"
D City walk is equally important to nature walk.