The present research project aims to compare the efficacy and safety of an intervention based on a smartphone application, which uses CBT techniques, to online group cognitive behavioral therapy (CBCT), in improving depressive symptoms.

The project also has supplemental analysis to predict who will respond to the CBT intervention using the application. For this analysis, machine learning algorithms, a set of techniques from the field of artificial intelligence, will be used to create a predictive calculator for response to interventions. The analysis protocol used for this analysis will be in accordance with that proposed in task Force of the International Society for Bipolar Disorders.

This is a randomized, non-inferiority, three-arm clinical trial, one of which consists of a waiting list. Participants in this study will be selected from an online survey already carried out and approved by the National Research Ethics Committee (Conep), which included 5,000 participants. Patients will be randomized to one of the study arms, application (Thrive) or CBCT (immediate start versus waiting list). Digital interventions in mental health have been gaining strength in the scientific literature, and recently the US Food and Drug Administration (FDA) authorized the digital prescription of an app to treat insomnia. This type of intervention is not a substitute for clinical consultation, but it can be useful in circumstances related to poor access to mental health services, which is a chronic problem in many developing and underdeveloped countries, but which has been exacerbated recently with the COVID-19 pandemic. 19. Of note, CBT is a first-line treatment for combating depressive symptoms, and its use has recently been studied on digital platforms. To help participants in this stage and increase their engagement, the app will provide access to a virtual caregiver and gamification strategies as reported in a recent editorial published in a famous scientific journal.

For this clinical trial, 400 participants with the expected symptoms among those who responded to the aforementioned clinical trial will be invited to be surveyed (National Trial Committee Survey Approved in Research Conducted and Approved).

The goals of this article will not be carried out in the main scientific journals of medicine, but also to assess whether a low-cost digital intervention designed only for reviews where the improvement in mental health is low may the altered symptoms of the included access . It is important that this intervention is useful not only in periods of social isolation, but also when the pandemic ends, since 1) about 50% of patients with depression do not have consultations with mental health professionals; 2) we expect an increase in the number of people with depression after the pandemic, due to its consequences.

Our hypothesis is that the smartphone application, with CBT techniques, although it does not replace the face-to-face consultation, is safe and is not inferior to the CBCT. If shown to be effective, this app will be an innovative, low-cost strategy for dealing with depressive symptoms during and after the pandemic.

Inclusion Criteria:

• have depressive symptoms characterized by PHQ-9≥9 and a diagnosis of Major Depressive Episode through the Mini-International Neuropsychiatric Interview instrument -- own a smartphone
• agree with the treatment objectives and sign the consent form
• age between 18 and 65 years
• be living in Brazil and be fluent in Portuguese.

Exclusion Criteria:

• pregnancy
• initiation of any psychological treatment within the previous 3 months
• visual impairment that prevents use of the app
• current risk of suicide
• bipolar disorder, schizophrenia, schizoaffective disorder, intellectual disability, and alcohol or drug abuse in the last year.

Other comorbid medical conditions will also be included, unless they are degenerative (dementia or multiple sclerosis) in a way that could compromise interaction with the application. Participants may be taking psychotropic drugs, including medication for depression, if the medication regimen has not changed in the previous 3 months and if there has been no change over the course of study participation.