Combining Metacognitive Therapy and tDCS: preliminary results in patients with Major Depressive Disorder

Background and aim: Transcranial direct current stimulation (tDCS) and metacognitive therapy (MCT) can reduce depressive symptoms as monotherapies or associated with pharmacological treatment. Here, we investigated the effectiveness of combining these treatments in a group of patients with major depressive disorder (MDD). Methods: So far, fourteen participants (10 females, Mage 43 ± 12) out of N= 54 estimated sample size were recruited at the Department of Neuroscience and Mental Health – Fondazione IRRCS Ca’ Granda Ospedale Maggiore Policlinico of Milano. All participants were under pharmacological treatment. They were randomly assigned to three groups receiving (i) real tDCS + sham MCT (n= 7); (ii) sham tDCS + MCT (n = 6) (iii) real tDCS + MCT (n= 1). The treatment lasted eight weeks, in which participants had one weekly MCT (groups ii and iii) or clinical interview session (group i) following the tDCS. TDCS was combined with attentional training (20 minutes, 1.5 mA, anode over the left dorsolateral prefrontal cortex) and took place three times a week for the first three weeks and then once a week. Clinical standardized questionnaires measuring depressive symptoms, anxiety, worry, rumination, and meta-beliefs were administered before and after the treatment, two weeks, three, six, and twelve months after treatment’s end. Results: Due to sampling distribution, mixed effects models were run, including time and only two groups as fixed factors (i and ii) and participants’ random intercept. Outcome measures revealed an effect of time, showing symptoms reduction after the treatment. Crucially, our results suggested a more robust reduction of worry and negative beliefs in the group receiving MCT compared to the one receiving only tDCS. Conclusions: despite preliminary, our results suggest that MCT can effectively reduce core symptoms contributing to the development and maintenance of MDD. Completing data collection will allow disentangling whether tDCS can boost this effect.