Spending more time outdoors in nature, particularly in green spaces such as gardens, is tied to better mental health and fewer sleepless nights, according to new research from an international group of scientists.

The study was led by Margarita Triguero-Mas, of the Barcelona Institute for Global Health, and was a collaboration with scientists in four European countries and the United States, including Edmund Seto, associate professor of environmental and occupational health sciences at the University of Washington School of Public Health.

The group conducted a nested cross-sectional study of 406 people in Barcelona, Spain; Stoke-on-Trent, United Kingdom; Doetinchem, Netherlands; and Kaunas, Lithuania. Researchers explored participants’ exposure to natural outdoor environments, including residential availability and nature contact, and different indicators of mental health.

Findings, published online Sept. 19 in the journal Environmental Research, showed no significant links between mental health and the amount of nature in residential areas. However, contact with nature, especially in “surrounding greenness,” was significantly tied to better mental health. Surrounding greenness included all types of green spaces, including those that were private and/or small such as urban gardens and street trees. People who had contact with surrounding greenness were 92 percent more likely to sleep well.

Another measure of exposure was to green and blue spaces, which referred to publicly accessible spaces larges than 0.5 hectares (or more than 1.2 acres).

Furthermore, evidence showed that the relationship was stronger for males, younger people, those with low-medium education and residents of Doetinchem, Netherlands. Findings also showed that scores of psychological well-being, vitality and having no medical symptoms were between 0.92 and 5.38 higher in people with surrounding greenness contact.

Geographic Information Systems, or GIS, was used to measure the amount of nature in participants’ residential areas and smartphone data was used to measure participants’ contact with the natural outdoor environment. Self-reported information was collected for mental health, including psychological well-being, sleep quality, vitality and somatization.

“Population mental health could benefit from environmental interventions aiming to increase public contact with natural outdoor environments,” the researchers wrote. “In particular, our data suggest focusing on surrounding greenness contact and natural outdoor environment characteristics that enhance stress reduction.