The effect of therapeutic horticulture on non-suicidal self-injury in adolescents with major depressive disorder: protocol for a randomized controlled trial.

Background: In recent years, the rising incidence and comorbidity of major depressive disorder (MDD) and non-suicidal self-injury (NSSI) among adolescents have emerged as a critical global public health challenge. Existing interventions often face limitations such as low patient willingness and poor adherence, restricting their effectiveness. This situation creates an urgent need to explore effective and acceptable interventions. Therapeutic Horticulture (TH) is a novel treatment that uses plant cultivation and related gardening activities as a therapeutic medium. It engages patients in planting, nurturing, and harvesting plants to achieve therapeutic effects. While it shows promise for adolescents with MDD, its efficacy specifically in adolescents with comorbid MDD and NSSI remains unclear. Therefore, this trial aims to evaluate the effects of TH on NSSI and psychosocial functioning in adolescents with MDD. Methods: This is a single-center, block-randomized, two-arm parallel randomized controlled trial (RCT) will be conducted at the Brain Hospital Affiliated with Guangzhou Medical University, Guangdong, China. Sixty-six participants will be allocated to an intervention or control group via block randomization. Inclusion criteria are (1): diagnosis of MDD and NSSI per DSM-5 criteria; (2) aged 12-18 years; (3) provision of informed consent; and (4) adequate comprehension, communication, and writing abilities. Exclusion criteria include comorbid other mental disorders, history of serious physical illness, receipt of systematic horticultural therapy within the past three months, allergies, or suicidal risk behaviors.The control group will receive treatment as usual. The intervention group will receive TH in addition to treatment as usual for two weeks. The primary outcome is the severity of NSSI. Secondary outcomes include depression, alexithymia, self-efficacy, sleep quality, and loneliness. All outcomes will be assessed at baseline (T Discussion: This study will investigate the application of TH in adolescents with comorbid depression and NSSI. The findings may offer a novel treatment option for this population and provide evidence for future clinical interventions and research. Trial registration: https://clinicaltrials.gov/study/NCT07115381. ClinicalTrials.gov identifier NCT07115381. Registered on 11 August 2025. Protocol version: 1.0, dated 31 October 2024.