Here is the design of a clinical trial:

Official Title: Effectiveness and Cost-effectiveness of a Lifestyle Modification Program in the Prevention and Treatment of Subclinical, Mild and Moderate Depression in Primary Care: A Randomized Clinical Trial Protocol

Included conditions:
- Depression

Study Armgroups:
- {'label': 'Control (TAU)', 'type': 'NO_INTERVENTION', 'description': 'Patients will follow the usual treatment provided by their GP (treatment-as-usual, TAU).'}
- {'label': 'Lifestyle Modification Program (LMP)', 'type': 'EXPERIMENTAL', 'description': 'It will consist of 6 weekly group sessions (lasting 90 minutes each).', 'interventionNames': ['Behavioral: Lifestyle Modification Program (LMP)', 'Behavioral: Lifestyle Modification Program (LMP) + Information Communication Technologies (ICTs)']}
- {'label': 'Lifestyle Modification Program (LMP) + ICTs', 'type': 'EXPERIMENTAL', 'description': 'It will consist of 6 weekly group sessions (lasting 90 minutes each).', 'interventionNames': ['Behavioral: Lifestyle Modification Program (LMP) + Information Communication Technologies (ICTs)']}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Lifestyle Modification Program (LMP)', 'description': 'Patients will follow TAU and LMP. This program will consist of 6 weekly group sessions (lasting 90 minutes each) led by an experienced psychologist and complemented by PowerPoint presentations. The content is the following:\n\n1. Presentation of the project and psychoeducation on depression.\n2. Behavior activation.\n3. Sleep hygiene habits and careful exposure to sunlight.\n4. Physical activity.\n5. Adherence to the Mediterranean diet.\n6. Summary of previous sessions with practical final suggestions.', 'armGroupLabels': ['Lifestyle Modification Program (LMP)']}
- {'type': 'BEHAVIORAL', 'name': 'Lifestyle Modification Program (LMP) + Information Communication Technologies (ICTs)', 'description': 'Patients will follow TAU and LMP and will be monitored using a wearable smart wristwatch that will track their daily sleep patterns and physical activity (LMP+ICTs).', 'armGroupLabels': ['Lifestyle Modification Program (LMP)', 'Lifestyle Modification Program (LMP) + ICTs']}

Primary Outcomes:
- {'measure': 'Beck II Self-Applied Depression Inventory (BDI-II)', 'description': 'The primary outcome will be measured using the BDI-II (Beck et al., 1996). This is a self-report inventory for measuring the severity of depression, consisting of 21 multiple-choice questions with each answer being scored on a scale ranged from 0 to 3. It was translated and validated into Spanish with a reliability of .89 (Sanz et al., 2005). The standardized cutoffs are: 0-13: minimal depression; 14-19: mild depression; 20-28: moderate depression; 29-63: severe depression.', 'timeFrame': 'Change from baseline, immediately after the intervention and at six and 12-month follow-up.'}

Please estimate the sample size based on the assumption: 
Significance level (α) of 0.05, power (β) of 0.20, and an estimated withdrawal rate of 20%.
Sample size
        Scientific evidence suggests that a 17% reduction in the BDI-II34 is considered clinically relevant.36 In a previous study conducted by our team with psychiatric outpatients, we found that the average BDI score at the beginning of the study was 24.5 points (SD 9.8),22 so we consider that a reduction of at least 4.8 points would have clinical significance and would benefit the patient. Accepting an Î± risk of 0.05 and a Î² risk of 0.20 in a bilateral contrast, 44 subjects will be required for each group. With an estimated withdrawal rate of 20%, the sample size will require approximately 53 patients in each group. The total sample required is 159 subjects. A formula based on the Snedecorâs F distribution37 has been used (see online supplemental file 2). It is estimated that approximately 50% of these patients will present some physical or mental comorbidity.12
        
          10.1136/bmjopen-2020-038457.supp2
          Supplementary data