Adding Anodal Transcranial Direct Current Stimulation to Mindfulness Meditation Abolishes Mindfulness-induced Improvements in Emotion Regulation in Fibromyalgia

Objectives: Mindfulness-based interventions (MBIs) seem to improve emotion regulation (ER) in disorders involving emotional dysregulation like fibromyalgia. Despite the therapeutic potential of transcranial direct current stimulation (tDCS) in fibromyalgia, its concurrent application with mindfulness meditation (MM) has not yet been explored. Potential synergistic effects may arise from aligning neural mechanisms underlying both interventions. This study evaluated the impact of a four-week MBI and a combined tDCS and MM intervention on ER, implementing a responder analysis approach. Methods: Following the MBI, 40 participants were randomly allocated to receive 10 days of 20-min MM combined with either anodal tDCS of the primary motor cortex (M1) or sham tDCS. ER was gauged using a composite score integrating four self-report questionnaires. We performed assessment at six time points (baseline, post-MBI, immediately post-combined intervention, 4-week, 8-week and 12-week follow-ups). Clinical responders were defined as patients exhibiting a clinically relevant reduction in fibromyalgia symptom load. Results: Responders to the MBI showed better ER than non-responders, lasting for six weeks. Interestingly, responders to the combined intervention in the sham group reported larger improvements in ER than non-responders, which was not observed in the anodal tDCS group. No significant interaction between responder status and time was found for responders to either intervention. Discussion: Our findings evidence that mindfulness practice is able to improve ER in fibromyalgia. However, the add-on combination of MM with M1-tDCS abolishes this mindfulness-induced effect. Therefore, based on our data, combining MM and M1-tDCS must be reconsidered as a therapeutic intervention targeting ER in fibromyalgia.