Depression is a highly disabling disease that is prevalent throughout the world. The treatments proposed and studied to date have shown to be partially effective in treating this condition. Neuromodulation strategies have been used as an alternative, especially for refractory and challenging cases. In this context, studies investigating the effectiveness of transcranial magnetic stimulation, including the theta burst stimulation (TBS) modality, have been increasing in number. However, there is still a lack of information seeking to explore the maximum effectiveness in the TBS modality. Therefore, the investigators developed a new stimulation protocol consisting of 3 TBS sessions per day, with an offer of 1200 pulses per session and a 30-minute interval between sessions. The protocol will be performed for 15 days, totalizing 45 stimulation sessions. The stimulations will be directed to the left dorsolateral prefrontal cortex (F3) and will be performed in a Magventure MagPro R30 device. The investigators will select 100 patients with unipolar major depression, following previously established inclusion and exclusion criteria, and will apply the protocol randomly, dividing the patients into an active and placebo group. The research team hypothesized that the active group patients will have greater improvement in symptoms of depression assessed by the 17-item hamilton depression scale over patients of the placebo group. In addition, other scales will be used for secondary outcomes. The researchers also hypothesized that there will be no difference between patients placed in the active or placebo groups in terms of side effects.

Depression is a highly disabling disease that is prevalent throughout the world. The treatments proposed and studied to date have shown to be partially effective in treating this condition. Neuromodulation strategies have been used as an alternative, especially for refractory and challenging cases. In this context, studies investigating the effectiveness of transcranial magnetic stimulation, including the theta burst stimulation (TBS) modality, have been increasing in number. However, there is still a lack of information seeking to explore the maximum effectiveness in the TBS modality. Therefore, the investigators developed a stimulation protocol consisting of 3 TBS sessions per day, with an offer of 1200 pulses per session and a 30-minute interval between sessions. This protocol will be applied to patients for 15 days, totaling 45 stimulation sessions. The stimulations will be directed to the left dorsolateral prefrontal cortex (F3 obtained by the Beam method) and will be performed in a Magventure MagPro R30 device.

The stimulation will be delivered at 100% of the motor threshold and will last for 6 minutes. The placebo will consist of a noise generator, which makes the same noise as active stimulation, and a surface electrode placed over the patient's eyebrow, mimicking the tactile sensory effects of TBS. The researchers will select 100 patients with unipolar major depression, following previously established inclusion and exclusion criteria, and the protocol will be applied randomly, dividing the patients into an active and placebo group. Inclusion criteria are: patients with a diagnosis of unipolar major depression confirmed by the Mini International Neuropsychiatric Interview (MINI), between 18 and 59 years of age, with a Hamilton score equal to or greater than 17. In addition, patients must have undergone at least 1 first-line treatment for depression and a maximum of 3 previous unsuccessful treatments. Exclusion criteria are: other mental disorders (bipolar affective disorder, obsessive-compulsive disorder, attention deficit hyperactivity disorder, personality disorders, substance use disorder, psychotic disorders), history of suicide attempts or severe suicidal ideation in the last 6 months. In addition, patients who have a history of epilepsy, decompensated medical conditions, metallic implants in the skull or previous experience with transcranial magnetic stimulation will be excluded.

The investigators hypothesized greater improvement in the symptoms of depression in patients of the active group compared with the placebo group, assessed by the 17-item hamilton depression scale. In addition, other scales for secondary outcomes wil be used, such as the Montgomery-Asberg Depression Scale. The research team also hypothesized that there will be no difference between patients in the different groups in terms of side effects. In the patient selection process, individuals will be evaluated and submitted to questionnaires in consultations by video call with a medical doctor of the research team. During the study, patients will be evaluated weekly and in person, by professionals who are not part of the stimulation application group. The service's waiting room will be organized in a certain way, so that patients do not meet or communicate during the study. After the end of the stimulations, the patients will be followed up for another 2 weeks in order to evaluate the support of the response obtained during the investigation. All data will be stored in a secure database with an external hard drive. All ethical considerations will be discussed with patients and followed during the study. The project has already been approved by the ethics committee of the Hospital of Clinics of the University of Sao Paulo. A pilot study will be conducted to assess the feasibility of the protocol.

Inclusion Criteria:

• Inclusion criteria are: patients with a diagnosis of unipolar major depression confirmed by the MINI interview, between 18 and 59 years of age, with a Hamilton score equal to or greater than 17. In addition, patients must have undergone at least 1 first-line treatment for depression and a maximum of 3 previous unsuccessful treatments.

Exclusion Criteria:

• Exclusion criteria are: other mental disorders (bipolar affective disorder, obsessive-compulsive disorder, attention deficit hyperactivity disorder, personality disorders, substance use disorder, psychotic disorders), history of suicide attempts or severe suicidal ideation in the last 6 months. In addition, patients who have a history of epilepsy, decompensated medical conditions, metallic implants in the skull or previous experience with transcranial magnetic stimulation will be excluded.

Participant data can only be accessed by study members. Such data will be stored in a database with an external hard drive (HD). The only way to access this database is to be affiliated with the institution where the study will be conducted and to request authorization from the study director, who coordinates access for the other researchers.

During the study, each participant will be evaluated by a single professional and this professional from the research group will be the only one with conditions to add or change clinical data according to evaluation.

After data analysis and the end of the research, supplementary materials containing a database preserving the anonymity of the participants will be made available.