Experiment reveals that a one-hour walk in nature reduces amygdala activity, which may protect mental health

A new study published in the journal Molecular Psychiatry offers evidence that a simple walk in nature can reduce activity in brain regions related to stress. The experiment revealed that participants who walked for an hour in a forest showed decreased amygdala activity during a stress task, while those who walked for an hour in the city did not.

Natural environments are known to provide mental health benefits. For example, being close to nature can reduce negative emotions and stress. On the other hand, psychologists have long argued for a connection between urban life and poor mental health. For example, city dwellers have higher rates of anxiety, depression, mood disorders, and schizophrenia than people who live in rural areas.

With the rise of urbanization, it is important to consider how natural and urban environments may impact the brain differently. There is some evidence that city dwellers show greater amygdala activation during social stress tasks compared to rural dwellers. In light of such findings, the study’s author Sonja Sudim and colleagues conducted an intervention study to investigate how a walk in nature compared to the city might affect brain regions related to stress. The researchers hoped to separate the negative effects of urban environments and the beneficial effects of nature.

“There has been strong research showing that exposure to nature is beneficial for mental health and cognition, but no study so far has examined the neural mechanisms behind these effects,” Sudimac explained.@sudimac), a doctoral student at the Max Planck Institute for Human Development in Berlin.

“In a pivotal study, a brain region involved in stress processing, the amygdala, was shown to be less activated during stress in people living in rural areas compared to those living in cities, which suggests the potential benefits of nature (Lederbogen et al., 2011). But until now it has not been possible to tease out the chicken-and-egg problem, that is, whether nature actually caused the effects on the brain, or whether particular individuals chose to live in rural or urban regions.”

“That is why we conducted an intervention study in which we were able to show causal evidence, that is, amygdala activity remained stable after a walk in an urban environment, while a walk in nature markedly reduced activity. of the amygdala”, explained Sudimac.

A total of 63 subjects with an average age of 27 years were recruited from Berlin to participate in the experiment. About half of the sample were randomly assigned to take a one-hour walk through an urban forest in Berlin, while the other half were assigned to take a one-hour walk down a busy street in one of the city centers. of Berlin. Before and after the walk, participants underwent functional magnetic resonance imaging (fMRI) while participating in a social stress task as well as a fearful faces task that measured amygdala activity in response to neutral or neutral facial expressions. fearful.

The results revealed that participants who took the nature walk showed decreased amygdala activity after the walk, both during the fearful faces task and during the social stress task. Those who walked around the city, however, showed stable amygdala activity during both tasks. The study authors say these findings suggest that exposure to nature promotes recovery from stress by reducing amygdala activity. Exposure to urban environments, on the other hand, neither decreases nor increases amygdala activity.

“We predicted that a walk in nature would decrease amygdala activity, while a walk in an urban setting would increase it,” Sudimac said. “However, we were surprised that a walk around the city did not cause additional stress-related brain activity. Brain activity in these regions remained stable after urban walking, which goes against the common view that urban exposure causes additional stress.”

Interestingly, the results of the fearful faces task were consistent for both masked and unmasked faces: amygdala activity decreased after the nature walk and remained stable after the city walk for both types of faces. . Masked faces are stimuli designed to be processed outside of participants’ awareness, so these findings suggest that people may not be aware of the stress-reducing effects of nature.

“Going for a walk in nature is beneficial for our mental health and our brain,” Sudimac told PsyPost. “Although many studies have shown that nature is good for our well-being, we found for the first time a causal link between exposure to nature and a reduction in stress-related brain activity. Interestingly, this effect was found only after one hour of walking, so if one doesn’t have time to spend a whole day in nature, it seems that just one hour is beneficial for our brain.”

Sudimac and colleagues discuss the possible implications of their study. The results suggest that spending more time in nature could increase the amygdala’s activation threshold, leading to reduced amygdala activity during stress. This means that exposure to nature could buffer the negative impact of urban life and reduce the risk of mental disorders among city dwellers. The study authors insist that urban planning must include efforts to modify and design cities with better access to green spaces to protect and improve the mental health of residents.

“We hope with our study to raise awareness about the importance of accessible green areas in cities,” said Sudimac.

One task for future research could be to hone in on the specific aspects of nature that reduce amygdala activity, for example sights, sounds, and smells. Studies could also compare the effects of particular types of natural settings, such as urban parks versus botanical gardens.

“We are also interested in different populations and age groups and are currently looking at data from our latest study on how an hour-long walk in natural versus urban settings impacts stress in mothers and their babies,” Sudimac said.

“I would like to add that these findings are also important because they confirm the importance of accessible green environments in cities,” he continued. “With more than half of the world’s population living in cities and urbanization increasing rapidly, it is essential that urban dwellers have a nearby park or forest where they can recover or ‘recharge’ from the stressful urban environment. With our research, we aim to draw attention to the importance of the presence of nature in urban environments and to provide evidence for urban design policies to create more green areas in cities that are accessible to all citizens in order to to improve your mental health and well-being. .”

The study, “How nature nourishes: the activity of the amygdala decreases as a result of an hour’s walk in nature”, was written by Sonja Sudimac, Vera Sale and Simone Kühn.