Here is the design of a clinical trial:

Official Title: Effectiveness of a Brief Psychological Mindfulness Based Intervention for the Treatment of Depression in Primary Care: Face-to-face Application, Treatment as Usual and Application Through ICTs

Included conditions:
- Depressive Disorder

Study Armgroups:
- {'label': 'TAU+mindfulness applied face to face', 'type': 'EXPERIMENTAL', 'description': '4 sessions of 90 minutes/session Mindfulness based intervention applied in groups of 10-12 people in traditional format. Written material and sound recordings will be offered as support elements. The estimated duration of the face to face program is one month.', 'interventionNames': ['Behavioral: Mindfulness']}
- {'label': 'TAU + Mindfulness ICTs intervention', 'type': 'EXPERIMENTAL', 'description': '4 sessions of 60 minutes/session Mindfulness based intervention applied by ICTs (Internet-based program). The online intervention will be individual and interactive, which will be supported by multimedia material (videos, sound recordings, etc.) and will have internet support. The estimated duration of the online program is two months.', 'interventionNames': ['Behavioral: Mindfulness']}
- {'label': 'Usual medical treatment (TAU)', 'type': 'NO_INTERVENTION', 'description': 'In this group the general practitioner will apply the usual treatment (medication) but there will be no psychological treatment.'}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Mindfulness', 'armGroupLabels': ['TAU + Mindfulness ICTs intervention', 'TAU+mindfulness applied face to face']}

Primary Outcomes:
- {'measure': 'Beck Depression Inventory-II', 'timeFrame': 'Baseline'}
- {'measure': 'Beck Depression Inventory-II', 'description': 'In the mindfulness-based intervention applied by ICTs', 'timeFrame': 'Post-treatment 8 weeks from baseline in 8 weeks intervention group'}
- {'measure': 'Beck Depression Inventory-II', 'description': 'In the mindfulness-based intervention applied face-to-face and TAU group', 'timeFrame': 'post-treatment 4 weeks from baseline in 4 weeks intervention group'}
- {'measure': 'Beck Depression Inventory-II', 'timeFrame': 'Six-months follow-up'}
- {'measure': 'Beck Depression Inventory-II', 'timeFrame': 'Twelve-months follow-up'}

Please estimate the sample size based on the assumption: 
We assumed a 5% significance level, 80% statistical power, a 1:1:1 ratio, a baseline correlation of 0.6, a decay rate of 0.35, a common SD of 5, and a dropout rate of approximately 20%.
Sample size
        The sample size estimation was based on testing whether the trend in the change is different between the intervention groups throughout the 4 time points. Firstly, we assumed that MBI groups would be able to present moderately high effects, compared to âTAU aloneâ, on the BDI-II at post-treatment. To operationalize this, we considered a standardized difference between arms on the main outcome of dâ=â0.7, which corresponds to the average effect observed in ten studies comparing MBIs with different wait-list conditions [36] and surpasses the 0.5 standard deviation criterion considered clinically relevant in previous studies [37, 38]. A preceding study by our research group with mild or moderate depressed patients in a similar Spanish PC setting found BDI-II means and standard deviations (SDs) of 22 and 5, respectively [20]. The inclusion criteria used in this study restricted the entry of mild or moderate depressed patients, thus reducing the SD compared to the general population and presenting a less skewed distribution of the data, as we predict will occur in the present study. The effect size referred to above corresponds to a difference of 3.5 points, which implies a reduction of slightly more than 15% in the BDI-II scale used. According to the GLIMMPSE v2.0.0 â time x group interaction in a general linear repeated measures (RM) design â and GPower v3.1.9.4 â ANOVA test for RM within-between interaction â statistical tools, considering the referred difference between the âface-to-face MBI + TAUâ vs. âTAU aloneâ groups of depressed patients, which corresponds to a partial eta square value of roughly 0.09 and an effect size f of 0.31, with a common mean at baseline of 22, a mean at post-test of 16 and 19.5 respectively, and a mean at post-test of 17 for the âInternet delivered MBI + TAUâ condition, and assuming a one point reduction in each group at each following time point, a baseline correlation of 0.6 and a decay rate of 0.35, assuming a common SD of 5, a 5% significance level, a statistical power of 80% using a 1:1:1 ratio, and an univariate approach to RM with Greenhouse-Geisser correction [39], we needed 33 subjects in each group. Because we expected a dropout rate of approximately 20% [40], we inflated the numbers to reach a total sample size of 120 patients, 40 per arm [41].