An observational feasibility study on the impact of green exposure on major depressive episode symptomatology and inflammatory biomarkers

Introduction: Major depressive and bipolar disorders are prevalent mental health conditions sharing the presence of major depressive episodes (MDEs). While psychopharmacological and psychological therapies are first-line treatments for MDEs, the response is often incomplete. New approaches focused on the human-nature relationship might complement antidepressant treatments, improving response. Methods: This observational pilot study aims to assess the feasibility of implementing regular exposure to green environments such as woods, forests, large parks, and gardens for at least forty-five minutes twice a week in a sample of patients experiencing a MDE who require adjustments to their antidepressant therapy. It also has the purpose of detecting changes in symptoms and inflammatory biomarkers at follow-up after six weeks. Results: Fifty-three patients were evaluated at the baseline; thirty-one completed the study. Nineteen (61%) of the completers reported regular exposure to greenery during the study. At follow-up, actively exposed patients showed trends of improvements in depressive symptoms, lower levels of C-reactive protein and interleukin-6, and higher adiponectin concentrations. Discussion: This result suggests that incorporating green exposure into clinical practice is feasible and potentially useful. However, more rigorous evaluations on larger samples are needed to verify whether exposure to greenery may complement MDEs treatment and favorably impact MDE-associated inflammatory processes.