1 Department of Educational and Counselling Psychology, McGill University, Montreal, QC, Canada.
2 Department of Psychiatry, McGill University, Montreal, QC, Canada; Department of Psychiatry, Saint-Jérôme Hospital, Saint-Jérôme, QC, Canada.
3 Department of Educational and Counselling Psychology, McGill University, Montreal, QC, Canada; Hôpital en santé mentale Rivière-des-Prairies (CIUSSS-NIM), Montreal, QC, Canada.
4 Department of Psychology, Bishop's University, Sherbrooke, QC, Canada.
5 Department of Psychology, Université du Québec à Montréal, Montreal, QC, Canada.
6 Department of Psychiatry, McGill University, Montreal, QC, Canada.
7 Department of Psychology, Concordia University, Montreal, QC, Canada.
8 School of Criminology, University of Montreal, Montreal, QC, Canada; Research Center of the Montreal Mental Health University Institute, Montreal,

Background: While walking in nature has been shown to improve affect in adults from the community to a greater extent than walking in urban settings, it is unknown whether such benefits apply to individuals suffering from depression. Using a parallel group design, this randomized controlled trial examined the effects of a single walk in nature versus urban settings on negative and positive affect in adult psychiatric outpatients diagnosed with major depressive disorder (MDD).

Method: Participants recruited from a psychiatric outpatient clinic for adults with MDD were randomly assigned to a nature or urban walk condition. Thirty-seven adults (mean age = 49 years) completed a single 60-minute walk. Negative and positive affect were assessed using The Positive and Negative Affect Schedule or PANAS at 6 time points: before the walk, halfway during the walk, immediately post-walk, at home before bedtime, 24 h post-walk, and 48 h post-walk.

Results: Controlling for baseline levels of affect before the walk, individuals who walked in nature experienced overall lower levels of negative affect, F(1, 35.039) = 4.239, p = .047, compared to those who walked in urban settings. Positive affect did not differ across walk conditions.

Limitations: The generalizability of results are limited by the small sample size and the presence of more female than male participants.

Conclusions: Walking in nature might be a useful strategy to improve negative affect in adults with MDD. Future research should investigate different ways to integrate the beneficial effects of nature exposure into existing treatment plans for psychiatric outpatients with MDD.