Effects of Low-intensity Transcranial Magnetic Stimulation on Major Depressive Disorder, and on 5-hydroxyindoleacetic Acid and Brain-derived Neurotrophic Factor Levels

The goal of this randomised clinical trial is to evaluate the effects of transcranial magnetic stimulation (TMS) on major depressive disorder (MDD) and on the levels of 5-hydroxyindoleacetic acid (5-HIAA) and brain-derived neurotrophic factor (BDNF). TMS works to treat MDD by using low-intensity magnetic fields to modulate certain areas of the brain, activating them which can help improve the mood of those suffering from the disorder. Final metabolites of serotonin such as 5-HIAA and growth factors such as BDNF will also be studied before starting the intervention and at the end to check if there is a significant change in their concentration. Likewise, its safety will be evaluated by monitoring the symptoms that they present at the end of the intervention and one month later. The main questions that are intended to be answered are: * Does low-intensity TMS reduce depressive symptoms in patients with MDD? * Does low-intensity TMS significantly change the initial and final concentrations of 5-HIAA and BDNF? * What adverse effects might patients who are exposed to low-intensity TMS experience? The researchers will compare low-intensity and accelerated TMS with sham TMS to see if low-intensity TMS works to treat MDD. Participants: * Will undergo an initial clinical assessment to confirm the disorder, comorbidities, and general health status. * A 5 mL blood sample will be taken before starting the intervention. * Low-intensity TMS will be applied for 4 days, 5 daily sessions of 200 s with 10-minute intersession intervals at a field intensity of 2-4 milliTesla (mT) and frequency of 50 Hz in theta bursts. Symptoms will be monitored daily. * A 5 mL blood sample will be taken at the end of the intervention and general health status clinimetrics will be reapplied.