Modern times have seen a remarkable increase in city dwellers due to rising urbanization and rural-to-urban migration. Even though metropolitan areas typically offer greater wages and better resources for healthcare, education, and employment, stress and the accompanying mental health issues, including anxiety disorders, depression, and schizophrenia, are also more prevalent.
Several studies have indicated that nature is a crucial requirement for many people and essential to maintaining our physical, mental, and emotional well-being. There is, however, little information describing the causal relationships between exposure to urban vs. natural environments and stress-related brain regions, despite the overwhelming body of research linking nature to the well-being of mental health. Importantly, the earlier research does not distinguish between whether stress reduction following exposure to nature results from that exposure itself or merely from the absence of negative urban consequences.
To answer these concerns, the Lise Meitner Group for Environmental Neuroscience researchers used an fMRI intervention study to look at brain activity before and after a one-hour exposure to nature versus urban surroundings. They made several intriguing discoveries, which we shall discuss in this post.
Using functional magnetic resonance imaging, the researchers monitored brain activity in stress-processing regions in 63 healthy volunteers before and after they took a one-hour walk in the Grunewald forest or in a busy Berlin shopping street to determine the relationship between nature and mental health (fMRI).
To ensure that men and women were equally dispersed among both locations, the participants were pseudo-randomly allocated to either a walk in the countryside (32 participants) or an urban setting (31 participants). Additionally, it was ensured that the distribution of afternoon walks between groups was equal during randomization.
Based on their data, the researchers found that the amygdala’s activity decreased following the nature walk, indicating that being in nature positively impacts brain areas associated with stress.
In the opinion of the researchers, the findings confirm the previously held belief that there is a beneficial relationship between nature and brain health, but this is the first investigation to establish a causative relationship. A prevalent belief that exposure to urban environments increases stress is refuted by the fact that the brain activity in these areas after the urban walk remained stable and did not exhibit increases.
Additionally, we discovered that amygdala activity when exposed to masked stimuli had the same result as exposure to unmasked stimuli: it was reduced after a natural stroll. Still, it stayed stable following a walk in an urban setting.
These findings are in line with earlier research indicating that the amygdala can be engaged in response to masked stimuli that participants were not aware of in the absence of cortical processing, and they imply that the stress-relieving benefits of exposure to nature may happen unnoticed.
The study’s findings demonstrate that being in nature benefits the parts of the brain responsible for processing stress and that this effect can be seen as soon as a one-hour walk. This advances our knowledge of how our physical living environment impacts our mental and cognitive wellness. Even a brief encounter with the outdoors reduces amygdala activity, suggesting that going for a walk in the woods can help protect against mental health issues and mitigate the negative effects of living in a city.
The study is the first to show the causal relationship between acute exposure to a natural vs. an urban environment on stress-related brain areas, separating nature’s benefits from the city’s drawbacks. The study’s results may shed light on the process underlying the environment’s cumulative impact on brain regions associated with stress.
Additionally, it underlines the significance of urban design guidelines that aim to increase the accessibility of green spaces in cities in order to improve residents’ mental health and well-being.
Sudimac, S., Sale, V., & Kühn, S. (2022). How nature nurtures: Amygdala activity decreases as the result of a one-hour walk in nature. Molecular Psychiatry. https://doi.org/10.1038/s41380-022-01720-6