Nature Therapy and Hypnotherapy for Patients with Mild to Moderate Depression – A Randomized, Three-Arm, Single-Center, Confirmatory, Controlled Study Using a Mixed-Methods Approach

INTERVENTION: Group 1: Arm 1: In addition to their standard routine care, patients in the nature therapy (NT) arm receive a total of 8 weekly sessions led by trained nature therapists in small groups (up to 10 patients) over an 8‐week period in an urban forest area. Each session lasts 90 minutes and includes training on how to perform the exercises independently. The weekly sessions consist of NT with a focus on nature‐focused sensory mindfulness exercises (perception of the five senses). Even after week 8, patients are encouraged to continue performing the exercises independently in nature. Group 2: Arm 2: In addition to the existing RV, patients in the hypnotherapy (HT) study arm receive a total of 8 weekly 90‐minute indoor HT sessions in small groups (up to 10 patients) led by group leaders with advanced training in hypnosis. In addition, they receive instructions and audio files of the hypnosis sessions for self‐administered practice (at least 3 times per week for 20 minutes each). The content of the hypnosis sessions involves visualizing nature combined with guided mindfulness exercises. The nature and mindfulness exercises are intended to be as similar as possible to the perceived nature and the mindfulness exercises performed in the nature therapy study arm. Even after week 8, patients are encouraged to continue using the hypnosis audio files for independent practice. Group 3: Arm 3: Patients in the control group (RV group) continue to receive only routine care over 16 weeks (continuation of existing psychotherapeutic treatment, such as behavioral therapy, depth psychology‐based or analytical psychotherapy; continuation of existing antidepressant medication in accordance with guidelines, including phytotherapeutic treatment, e.g., St. John’s wort). Stays in nature are document CONDITION: light to moderate depressions PRIMARY OUTCOME: Severity of depression as assessed by a blinded evaluator using the MADRS (Montgomery‐Åsberg Depression Rating Scale) after 8 weeks INCLUSION CRITERIA: A specialist diagnosis of mild to moderate depression according to the DSM‐5 criteria The patient’s willingness to be randomized and to participate in the interventions and examinations as part of the study, as well as to complete questionnaires and diaries Proficiency in the German language Intact hearing and speech comprehension Sufficient mobility to participate in nature therapy The patient is capable of giving informed consent and is cognitively and linguistically able to assess the significance of the study Signed informed consent form SECONDARY OUTCOME: ‐ Blinded external assessment of the severity of depression using the MADRS at Week 16 ; ‐ Depression assessed using the Beck Depression Inventory‐II (BDI‐II) at Weeks 8 and 16 ; ‐ Subjective stress perception using the Perceived Stress Scale‐10 (PSS), measurement points: Week 8, Week 16 ; ‐ Mental well‐being using the World Health Organization‐Five Well‐Being Inde X(WHO‐5) in the diary weekly during Weeks 1–8 at the end of each week and in the questionnaire after Week 16 ; ‐ Connection to nature using the Connectedness to Nature Scale (CNS) at Week 8 and Week 16 ; ‐ Mindfulness using the Mindful Attention and Awareness Scale (MAAS) at Week 8 and Week 16 ; ‐ Patients’ overall assessment of changes (PGI‐C), assessment points: Week 8 and Week 16 ; ‐ Treatment safety: The number and type of treatment‐related adverse events (UTW), adverse events (UE), and serious adverse events (SUE) are recorded and analyzed in the study diary throughout the entire study period between baseline and Week 8 and Weeks 9–16. Similarly, changes in medication or initiation of medication for the treatment of depression are documented weekly between baseline and week 16. ; ‐ Adherence to the study intervention: Frequency and duration of interventions measured by participation in the weekly sessions up to week 8, as well as the number of weeks with at least 3 independent exercises up to week 8 and in weeks 9–16; total number and duration of independent exercises per week up to week 8 and in week ; and in week 9‐16 ; Health economic issues: ; ‐ Health resources actually utilized (direct resource use, including medical consultations, hospital stays, drug therapies, and rehabilitation measures) ; ‐ Absences from work due to illness (indirect factors, particularly lost workdays) ; Additional assessments: ; ‐ Suggestibility in the HT study arm, measured using the Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS:A), is assessed at baseline and in the HT group after week 8. ; ‐ Concomitant medication/therapies for depression and nature stays during the study ; ‐ Concomitant medication/therapy for depression is documented in the diary during weeks 1–8 and weeks 9–16. ; ‐ Expectations: The baseline questionnaire includes questions regarding expectations regarding the study intervention and its efficacy.