An Empirical Study on the Mechanisms of Biopsychosocial Functional Improvement in Patients With Major Depressive Disorder Through Nature-Based Tourism Activities

Inclusion criteria

• Voluntarily participate in the study and sign the informed consent form;
• Age between 18 (inclusive) and 60 (exclusive) at the screening period;
• Meet the DSM-5 diagnostic criteria for a Major Depressive Episode (MDE) at enrollment, based on medical records, clinical assessment, and the Mini-International Neuropsychiatric Interview (MINI version 7.0.2);
• Hamilton Depression Rating Scale 17-item (HAMD-17) score ≥ 17 at both screening and baseline;
• Physically stable based on medical history and vital signs (including blood pressure);
• Deemed by the investigator to be capable of independently completing all assessment tools required by the study protocol and willing to comply with the trial procedures throughout the study period.

Exclusion criteria

• Current or past diagnosis of: schizophrenia, psychotic disorders (unless substance-induced or due to another medical condition), bipolar disorder, delusional disorder, paranoid personality disorder, schizoaffective disorder, borderline personality disorder, or other severe psychiatric comorbidities confirmed by medical history and structured clinical assessment using the Mini-International Neuropsychiatric Interview (MINI version 7.0.2);
• Current or history of alcohol or substance abuse within the past year;
• A score of ≥3 on item 3 (suicide) of the HAMD-17, suicide attempt within the past year, or clinically assessed significant suicide risk;
• Depression secondary to other severe medical conditions (e.g., hypothyroidism, Parkinson's disease, etc.);
• Cardiovascular diseases: stroke or myocardial infarction within the past year, hypertension (blood pressure \>140/90 mmHg), or clinically significant arrhythmia;
• Other significant comorbid diseases that may interfere with the interpretation of study results or pose risks to participant health (e.g., cardiovascular, respiratory, gastrointestinal, hepatic, renal, or other systemic diseases), as determined by the investigator;
• Current participation in an interventional study for Major Depressive Disorder, or participation in such a study within 30 days prior to screening;
• Having visited Wulongtan Park, Baotu Spring Park and Daming Lake Park for a prolonged period (single stay ≥1 hour) within the past three years.