Does attention matter more than exposure? A pilot RCT of nature-based mindfulness for mental well-being and stress.

Contact with nature supports psychological health, yet whether the quality of mindful engagement matters more than the quantity of exposure remains unclear. This pilot randomized controlled trial examined a brief, structured nature-based mindfulness program's effects on mental well-being, perceived stress, and nature connectedness relative to an unstructured outdoor walking control. Participants (N = 35) were randomly assigned to daily 15-min guided nature-based mindfulness sessions or daily unstructured outdoor walks over 2 weeks. Point estimates favored the intervention group for mental well-being and perceived stress, but neither group difference reached statistical significance, and the sample was well below what would be needed to detect effects of this magnitude with adequate power. Participants with lower baseline mental well-being achieved greater gains in the intervention group than participants with higher baseline well-being, an advantage not observed in the control group. Both groups increased in nature connectedness with no significant between-group difference; mediation analyses found no evidence that connectedness mediated intervention effects. The intervention group achieved these outcomes despite significantly less total nature exposure than controls, though duration was not independently manipulated. These preliminary findings may serve as hypothesis-generating for future, adequately powered trials.