This study is a single-blind, multicenter, randomized, controlled crossover trial. The App, developed in South Korea, is an application that provides integrated interventions for stress reduction for the general population. The App provides three contents based on MBSR, CBT, and relaxation sounds that are known to be effective in stress reduction ("Meditation category", "Cognitive approach", and "Relaxation Sound", respectively). Participants (n = 215) recruited via medical practitioner referral will be randomized to App first group (fAPP) or a waitlist crossover group (dAPP). Inclusion criteria are age 19-65; diagnosed with mild to moderate major depressive disorders (Score of 7-24 on the Hamilton Rating Scale for Depression); Stable medication for 28 days prior to study participation. The study was conducted over eight weeks, the fAPP group used The App for the first four weeks and the dAPP group for the next four weeks, and during all study periods, the participants received usual pharmacological treatment. Primary outcome measures are the Depression Anxiety Stress Scale-21. The analysis will use mixed-model repeated measures.

This study is a single-blind, multicenter, randomized, controlled crossover trial. All subjects who met the inclusion and exclusion criteria will be randomly assigned to the App first group (fAPP) and or a waitlist crossover group (dAPP). Due to the intervention's nature, this will be a single-blind study in which the results will be assessed blindly but participants will be aware of their group assignment. Participants assigned to fAPP group will use the App initially for 28 consecutive days (T1). During T1, participants assigned to the dAPP arm will maintain the usual treatment. After T1, during the next 28 consecutive days (T2) without washout period, dAPP will use the APP, and fAPP will only maintain the usual treatment. We assumed that there would be no carry-over effect as the App utilized in this study is not a curative treatment but rather a tool for relieving stress in patients with depression. Therefore, we decided to use a cross-over design without a wash-out period.

The three University Hospitals in the Republic of Korea participating in the study will recruit depressive patients for applying the App. The Korea University Guro Hospital and Korea University Anam Hospital are in the inner center of the Capital, and Korea University Ansan Hospital is in Ansan city, outskirts of the capital area. Each hospital is a general hospital, and the Korea University Guro Hospital will lead the ASMA-D study as. For patient recruitment, 96 patients (48 interventions and 48 controls) in the Korea University Guro Hospital and 60 patients (30 interventions and 30 controls) in each from Korea University Anam Hospital and Korea University Ansan Hospital will be expected.

Screening will begin for those who are interested in advertisements posted in the participating hospital among the depressive patients who visit the hospital. After interested patients will contact the research team. the patients will be screened for eligibility according to the above-described criteria by the psychiatrist. After eligibility is confirmed, details of study will be explained to potential participant. Once participant agrees to participate, Informed consent is obtained, patient is enrolled, and randomization only occurs after enrollment.

Successful volunteers will be randomly assigned to the fAPP of dAPP. Randomization is conducted using block randomization by each clinical center. To prevent bias towards one treatment group, eight patients will be configured in blocks and will be randomly assigned to groups fAPP and dAPP within each block. For consistent allocation, randomization will be done using a pre-built program. This program is created by Korea University Guro Hospital to blind the researcher from the information of assignment in advance.

Assessments are obtained clinician rating scale and self-rating scales during hospital visits. Assessments conducted at the hospital visit were acquired at the baseline (V0) and every two weeks (V1, V2, V3, and V4) during T1 and T2. The baseline assessments will be collected when participants are enrolled and include sociodemographic and clinical characteristics. All instruments have been translated to Korean with reliable psychometric properties. The data collection process implanted in the evaluation module of the mobile App will be activated through an ID issued after enrollment and randomization.

Inclusion Criteria:

1. Adults between the ages of 19 and 65;
2. Diagnosed with mild to moderate major depressive disorders in an expert interview evaluation according to the DSM-IV diagnostic criteria (Score of 7-24 on the Hamilton Rating Scale for Depression [HAM-D]);
3. Stable medication for 28 days prior to study participation;
4. Informed consent and voluntary participation.

Exclusion Criteria:

1. Hard to use smart phone or unable to independently use Application;
2. Diagnosed with severe major depressive disorder in an expert interview evaluation according to the DSM-5 diagnostic criteria (score of 25 or more on HAM-D);
3. Severe mental disorders (current or in the past), including Major depressive disorder with psychotic features, bipolar affective disorder, personality disorder, obsessive compulsive disorder, autism spectrum disorder, substance use disorder;
4. History of brain injury, epileptic seizures, intellectual disability, or cognitive disorders;
5. History of severe physical disorders, including cancer, tuberculosis, severe cardiovascular disease, etc.
6. Individuals participating in other cognitive behavioral therapy or activities related to stress relief

The datasets used and analyzed during the current study will be available from the corresponding author on reasonable request.

The time when all research processes have been completed and the relevant results are published.

Due to the intervention's nature, this will be a single-blind study in which the results will be assessed blindly, but participants will be aware of their group assignment. Most of the assessments are self-rated, and the clinician rating, HAM-D, will be assessed by an independent blinded evaluator not participating in the assignment and care providing.