Transcranial direct-current stimulation over the motor cortex in patients suffering from anxiety and depression related to rheumatoid arthritis: Study protocol for a randomized, double-blind, placebo-controlled trial.

Rheumatoid arthritis is up to three times more prevalent in women. It is often associated with anxiety and depression, comorbidities causing psychic suffering and potentiating pain perception. It is also related to a higher risk of suicide among diagnosed patients. The high rates of discontinuation of conventional pharmacological treatments are the predominant factor in the search for new therapeutic approaches for the treatment of anxiety and depression. Transcranial direct-current stimulation (tDCS) is a promising, safe and low-cost technique that is very associative with other therapies. When applied to the primary motor cortex (M1) it can induce long-term changes in the synaptic level leading to the improvement of neuroplasticity. The primary aim of this study is to evaluate the effect of tDCS on the symptoms of anxiety and depression. The secondary aim is to evaluate the interference of tDCS on the inflammatory profile, cardiac autonomic behavior and quality of life of patients with rheumatoid arthritis. This is a randomized, double-blind, placebo-controlled clinical trial. The intervention consists of 10 consecutive sessions (once a day) applying tDCS with a 2mA current for 20 minutes. The electrode assembly on the scalp is in accordance with the International Electroencephalogram System 10-20 (EEG) and the anodal electrode is placed over the area of the primary motor cortex (M1 - C3 or C4) and the cathodal electrode on the supraorbital contralateral area (SO - Fp1 or Fp2). The analysis of continuous variables will be described by mean and standard deviation for parametric data and median and interquartile interval for nonparametric data. The evaluation of the effect of tDCS on the inflammatory profile, heart rate variability and quality of life will be obtained by the ANOVA two-way test. tDCS is expected to have a greater effect on reducing anxiety and depression symptoms compared to the placebo, being able to decrease inflammation and improve the quality of life of volunteers.