Intervention
The gardening program was conducted from June to November 2022 as a group therapy with 30 sessions over 15 weeks, based on the suggested manual of the Korea National Arboretum in 11 green-area sites nationwide (e.g., botanical gardens, gardens in medical centers, and green areas in universities). The gardening program took place twice a week, with each session lasting around 2 h. The contents of the gardening program are presented in Supplementary Table In the control group, participants were not provided any nature-based activities or intervention. However, participants recruited from community centers participated in daily activities provided by their centers as usual (TAU) without engaging in any type of nature-based intervention. For example, older adults in senior center participated in group aerobic, singing or reading classes provided by community center as usual. In the case of students, they received vocational training such as computer programming, cook training, and service training. Participants who were recruited from medical center or mental health care center were provided medical care as usual.