- Living in cities can increase one's risk of developing anxiety, depression, and schizophrenia.
- A new study investigated the brain processes underlying the positive effects on stress of taking a walk in a forest.
- The results of the study showed that a walk in the forest reduces activity in the amygdala and benefits mental health.
Life in a large city can be incredibly stressful. Psychological research has shown that people who live in cities may have an increased risk for depression, anxiety, and schizophrenia compared to people living in more rural areas. In contrast, many people perceive hiking and spending time in nature as stress-relieving and calming. What has been largely unclear so far, however, is the question of how specifically spending time in nature affects our brain function to reduce stress.
The positive effects of nature on mental well-being
A new study, published in the journal Molecular Psychiatry (Sudimac et al., 2022), focused on precisely this question. In the study, entitled “How nature nurtures: Amygdala activity decreases as the result of a one-hour walk in nature,” a research team led by Sonja Sudimac from the Max Planck Institute for Human Development in Berlin investigated how stress-related brain regions reacted to a one-hour walk in an urban environment—a busy street in Berlin—compared to a natural environment; in this case, a forest.
The researchers used a neuroscientific technique called functional magnetic resonance imaging (fMRI) to measure brain activation in 63 healthy volunteers in two groups: walking in nature or walking in an urban environment. In both groups, brain activation was measured before and after the walk, using two different tasks in the MRI scanner. The first fMRI task was a fearful-faces task designed to activate anxiety-related brain networks, and the second fMRI task was a social-stress task designed to activate stress-related brain networks.
In the fearful-faces task, volunteers watched faces with fearful and neutral expressions while lying in the scanner. The so-called MIST (Montreal Imaging Stress Task) was used as the social stress task. In the MIST, volunteers have to solve very complicated mathematical tasks designed to be beyond their abilities, while they get compared to a fake "average." The fake average the volunteers see is always better than their own performance, so that they may feel stressed since they perform so badly.
Amygdala activity is reduced after a walk in nature
The scientists found very similar results in both the fearful faces and the stress test. For the group of volunteers that walked for one hour in an urban environment, there were no changes in the activation of fear or stress-related networks between the two scans. In contrast, for the group of volunteers that walked for one hour in nature, there was a decrease in activity in one specific brain area for both fMRI tasks after the walk: the amygdala; in particular, the right amygdala.
The amygdala is a group of neuronal nuclei within the temporal lobe of the brain and has been shown to be a key structure in the processing of fear and stress. In particular, when people are stressed out, their brains tend to switch to more amygdala-driven networks. The finding that amygdala activity reduces after a walk in nature, therefore, led the scientists to conclude that a walk in nature can help restore us from the negative effects of stress. This finding has powerful implications as it suggests that taking time off and hiking in the woods can have a protective effect on the development of many psychological disorders for which stress is often a major influence factor.
So what can you do the next time you feel stressed out? Take a hike in the woods, and you should feel a little less frazzled.
Sudimac S, Sale V, Kühn S. (2022). How nature nurtures: Amygdala activity decreases as the result of a one-hour walk in nature. Mol Psychiatry, epub ahead of print.