In recent times, the "20-minute park effect" has gained traction in urban circles—the idea that spending just 20 minutes in a park, even without exercise, can significantly lift one's mood. As noted by renowned science writer Zhang Tiankan, this concept, though initially seeming mysterious, is rooted in research published in the International Journal of Environmental Health Research. Its mechanism isn’t merely about pleasant surroundings or psychological suggestion; it’s deeply tied to human stress hormones.
The "20-Minute Park Effect" Goes Viral: Why Does Being Close to Nature Improve Mood?
Recently, a trend known as the "20-minute park effect" has become popular among urban dwellers. It suggests that even without any physical activity, simply spending 20 minutes in a park can make people feel happier. It's actually from a research paper published in the International Journal of Environmental Health Research. The reasons behind it are not just about the pleasant environment and psychological cues but are also closely tied to the body's stress hormones.
The "20-Minute Park Effect" Is Scientifically Confirmed
A good environment has a clear positive impact on mental well-being and can also affect the body, making people feel relaxed and energized. From this perspective, urban green spaces—such as parks, gardens, and other public areas covered with natural vegetation—serve as such beneficial environments, offering people a temporary escape from the hustle and bustle and a chance to connect with nature. But is it really true that just 20 minutes in a park, without doing anything, can make people happier?
The "20-minute park effect" isn’t just based on subjective feelings; it has been confirmed through psychological, physiological, and biochemical research.
In 2020, researchers from the University of Alabama recruited 98 adult visitors from three urban parks in Birmingham to investigate changes in their psychological state before and after their park visits. The researchers used a psychological research method called a "one-group pretest-posttest design," asking participants to complete questionnaires and wear pedometers to record their activity levels in the park. The results showed that visitors experienced significant improvements in mental health after their park visits, including mood and life satisfaction. However, because the study lacked physiological and biochemical evidence, it was criticized for insufficient scientific rigor.
To address these concerns, the same research team conducted a second study in 2023, focusing on physiological and biochemical validation of the "20-minute park effect."
In addition to questionnaires, they selected more urban parks of varying sizes and facilities to ensure the results were more representative. They also measured participants' physiological and biochemical indicators, primarily by collecting saliva samples to test levels of cortisol and dehydroepiandrosterone (DHEA)—hormones associated with stress.
Table : Characteristics and activity patterns of participants (N = 60)
The results showed that 76.7% of participants reported increased happiness after their park visit. Their mental health scores rose from an average of 35.82 before entering the park to 39.18 afterward, indicating a significant subjective improvement in well-being. More importantly, 78.3% of visitors showed a notable decrease in cortisol levels after their park visit, demonstrating effective stress relief. Additionally, the decline in DHEA levels was greater than what would occur naturally, with an average reduction of 27%.
Figure : The ability of park stay time to predict the improvement of cortisol levels after park visit, with an AUC value of 0.76, indicating a relatively high prediction accuracy
The researchers concluded that spending at least 21.8 minutes in a park could lead to measurable decreases in cortisol levels.
Thus, both psychological perceptions and physiological/biochemical indicators confirmed the positive impact of park visits on physical and mental health. Simplifying the complex scientific principles, it means that a short stay in a park can significantly reduce cortisol and DHEA levels in the body, and the decrease in these hormones alleviates stress.
How Stress Hormones Affect Mental State
Beneath the surface of subjective psychological experiences, cortisol and DHEA are the key biochemical foundations of happiness, with cortisol playing the most prominent role. It can increase blood glucose levels, supplying the energy needed for action. By converting fat and protein into glucose, cortisol ensures a steady supply of glucose to the brain (keeping it alert) while providing ample energy to muscles, the heart, and the lungs (enabling actions like running), increasing lung capacity and cardiac output to meet physical demands.
As the earlier study revealed, when the serene natural and cultural environment of a park gives people a sense of tranquility, it acts like an environmental sedative, rapidly reducing stress and cortisol secretion, bringing levels back to normal and thus improving mood.
In other words, any stressful event can cause cortisol levels to rise quickly. This is actually an evolutionary mechanism humans developed to cope with danger, prompting them to either confront or flee threats.
For example, chronically elevated cortisol levels can weaken the immune system, raise blood sugar and blood pressure, and lead to insomnia. More importantly, long-term high cortisol levels can harm mental health, keeping individuals in a constant state of tension that results in fatigue, irritability, depression, anxiety, and even post-traumatic stress disorder (PTSD). Conversely, moderate cortisol levels help people stay relaxed and perform better in learning or work. For instance, athletes perform better in competitions when they are not overly tense (moderate cortisol levels) but struggle when excessively stressed (high cortisol levels).
Therefore, in the fast-paced work environment, cortisol levels tend to be elevated. Taking just 20 minutes in a park can lower cortisol levels, thereby improving mood and creating a sense of comfort and happiness. This is the physiological and biochemical basis of the "20-minute park effect."
The 20-minute park effect is more than a trend; it’s a scientifically validated tool for reducing cortisol and improving mood. In today’s fast-paced urban life, taking short breaks in green spaces offers a simple yet powerful way to restore balance. As research continues to underscore the link between nature and health, integrating green infrastructure into cities becomes not just a luxury but a necessity for holistic well-being.
References
- Yuen, H. K., & Jenkins, G. R. (2020). Factors associated with changes in subjective well-being immediately after urban park visit. International Journal of Environmental Health Research, 30(2), 134–145. https://doi.org/10.1080/09603123.2019.1577368
- Gao, J., et al. (2023). Changes in cortisol and dehydroepiandrosterone levels immediately after urban park visits. International Journal of Environmental Health Research, 33(2), 206–218. https://doi.org/10.1080/09603123.2021.2013454
