Nature experience reduces rumination and subgenual prefrontal cortex activation

Abstract

Urbanization has many benefits, but it also is associated with increased levels of mental illness, including depression. It has been suggested that decreased nature experience may help to explain the link between urbanization and mental illness. This suggestion is supported by a growing body of correlational and experimental evidence, which raises a further question: what mechanism(s) link decreased nature experience to the development of mental illness? One such mechanism might be the impact of nature exposure on rumination, a maladaptive pattern of self-referential thought that is associated with heightened risk for depression and other mental illnesses. We show in healthy participants that a brief nature experience, a 90-min walk in a natural setting, decreases both self-reported rumination and neural activity in the subgenual prefrontal cortex (sgPFC), whereas a 90-min walk in an urban setting has no such effects on self-reported rumination or neural activity. In other studies, the sgPFC has been associated with a self-focused behavioral withdrawal linked to rumination in both depressed and healthy individuals. This study reveals a pathway by which nature experience may improve mental well-being and suggests that accessible natural areas within urban contexts may be a critical resource for mental health in our rapidly urbanizing world.

Keywords: emotion regulation; environmental neuroscience; nature experience; psychological ecosystem services; rumination.

Fig. S1.

Satellite maps of (A) the nature walk and (B) the urban walk. Both walks were a total of 5.3 km.

Fig. S2.

Sample photographs taken by participants during (A and B) the nature walk and (C and D) the urban walk.

Fig. 1.

The impact of nature experience on self-reported rumination and blood perfusion to the sgPFC. (A) Change in self-reported rumination (postwalk minus prewalk) for participants randomly assigned to take a 90-min walk either in a natural setting or in an urban setting. (B) A time-by-environment interaction in blood perfusion was evident in the sgPFC. F map of significant interactions at a threshold of P < 0.05, FWE corrected for multiple comparisons. (C) Change in blood perfusion (postwalk minus prewalk) for participants randomly assigned to take a 90-min walk either in a natural setting or in an urban setting. Error bars represent SE within subjects: *P < 0.05, ***P < 0.001.

Fig. S3.

All brain regions showing time-by-environment interaction (P < 0.05, FWE corrected). Slice coordinates from left to right: z = 1, x = 55, x = 5, y = 13, y = −52.

Fig. S4.

Quantum GIS (QGIS) maps of (A) the nature walk and (B) the urban walk. Fifty-meter buffer zones around the paths are shown in purple. Buildings and roads were used to calculate percentage of this buffer that consisted of impervious surface. To calculate percent imperviousness for each environment, we used QGIS (www.qgis.org) to create a buffer zone of 50 m around each walking path (i.e., center of El Camino Real and the center of the Dish trail). We then used combined building footprint and road data to calculate the amount of impervious surface contained within the total area of each 50-m buffer zone. Area within the buffer was then coded in a binary fashion as impervious or nonimpervious, resulting in a percentage of total buffer area that could be classified as impervious.