No add-on therapeutic benefit of at-home anodal tDCS of the primary motor cortex to mindfulness meditation in patients with fibromyalgia

•Comparing anodal tDCS paired with mindfulness meditation to sham tDCS in fibromyalgia.•Pain, quality of life and symptoms improve over time, independent of group with inconclusive mechanistic effects assessed by TMS.•Findings challenge paired tDCS and meditation in fibromyalgia treatment. This study investigated the efficacy of combining at-home anodal transcranial direct current stimulation (tDCS) of the left primary motor cortex (M1) with mindfulness meditation (MM) in fibromyalgia patients trained in mindfulness. Thirty-seven patients were allocated to receive ten daily sessions of MM paired with either anodal or sham tDCS over the primary motor cortex. Primary outcomes were pain intensity and quality of life. Secondary outcomes were psychological impairment, sleep quality, mood, affective pain, mindfulness level, and transcranial magnetic stimulation (TMS) measures of cortical excitability. Outcomes were analyzed pre- and post-treatment, with a one-month follow-up. We found post-tDCS improvement in all clinical outcomes, including mindfulness level, except for positive affect and stress, in both groups without significant difference between active and sham conditions. No significant group*time interaction was found for all clinical and TMS outcomes. Our findings demonstrate no synergistic or add-on efffect of anodal tDCS of the left M1 compared to the proper effect of MM in patients with fibromyalgia. Our findings challenge the potential of combining anodal tDCS of the left M1 and MM in fibromyalgia.