Efficacy of horticultural therapy on symptoms and functional outcomes in individuals with depressive disorders: A systematic review and meta-analysis of randomized controlled trials

Objective: This study evaluated the efficacy of horticultural therapy (HT) in improving affective symptoms and functional outcomes in individuals with depressive disorders. Methods: A systematic search was conducted across the PubMed, EMBASE, Cochrane Library, CINAHL, CEPS, CNKI, and Wanfang databases. Randomized controlled trials (RCTs) implementing HT were included. Outcomes assessed included differences between HT and control groups in depression, anxiety, physical function, cognitive function, social function, and quality of life. A random-effects model was used to calculate Hedges’ g. Risk of bias was assessed using the Cochrane Risk of Bias tool, and the certainty of evidence was evaluated using the GRADE approach. Results: Thirteen RCTs (n = 960) were included. HT significantly improved depression (g = 1.050; 95 % CI: 0.663–1.437), anxiety (g = 0.702; 95 % CI: 0.341–1.062), cognition (g = 0.816; 95 % CI: 0.302–1.331), social function (g = 0.806; 95 % CI: 0.295–1.317), and quality of life (g = 0.947; 95 % CI: 0.633–1.260). Only one study reported improvement in physical function. Subgroup analyses revealed greater effects among inpatients with more severe baseline symptoms who received combined indoor-outdoor HT in care-providing settings for more than eight weeks. However, the certainty of evidence across outcomes ranged from very low to low due to risks of bias, inconsistency, and imprecision. Conclusion: This review provides preliminary support for the efficacy of HT in depressive disorders. Given methodological limitations and potential biases, further well-designed trials with registration, blinded assessors, and long-term follow-up are warranted.