Impact of the Placebo Effect on the Effects of Trancranial Direct Current Stimulation in Fibromyalgia

Fibromyalgia (FM) is a syndrome characterized by generalized musculoskeletal pain, fatigue, non-restorative sleep, cognitive alterations, depressive and neurovegetative symptoms. Conventional pharmacological therapies are known to produce responses with little clinical impact in more than 50% of patients. Functional alterations of the motor cortex and its connections with subcortical structures have also been demonstrated in FM. Based on the above, the objective of this research is to identify subgroups of patients with greater potential for response to treatment with a view to advancing diagnosis and treatment. In this study, the therapeutic target will be transcranial direct current stimulation (tDCS) according to the potential of responsiveness to the placebo effect, with the precise location of the stimulation area by a neuronavigation system, with the objective of counter-regulating the processes dysfunctional factors responsible for triggering and maintaining FM symptoms. Therefore, this clinical trial aims to compare the effectiveness of anodal tDCS applied to the primary motor cortex (M1) compared to sham tDCS in FM, according to susceptibility to the placebo effect and serum endorphin levels.