BACKGROUND: Impaired plasticity has been implicated in major depressive disorder (MDD), which is reflected in impaired automatic sensory detection as measured using mismatch negativity (MMN). Intermittent theta-burst stimulation (iTBS) is used to treat MDD and its mechanism of action has been suggested to be plasticity dependent. Thus, we aimed at evaluating MMN as a MDD biomarker and predictor of antidepressant effect of iTBS. METHODS: This study comprised 46 patients with MDD and 64 healthy controls. The participants completed an auditory duration deviant MMN paradigm. In patients, MMN was recorded before and after a two-week intervention of twice-daily stimulation with a prolonged iTBS protocol, or sham, over the dorsomedial prefrontal cortex (DMPFC). Depressive symptoms were assessed with the affective subscale of the Brief Psychiatric Rating Scale (BPRS-affective) and through the self-report version of the Montgomery-Åsberg Depression Rating Scale (MADRS-S). RESULTS: There were no differences in MMN amplitude at baseline between patients and controls, nor any correlations between depressive symptoms and MMN amplitude. MMN amplitude did not change after iTBS. However, in the active iTBS group a larger baseline MMN amplitude correlated significantly with greater reductions of depressive symptoms following iTBS, Δ-MADRS-S (r = 0.48, p = 0.021) and Δ-BPRS-affective (r = 0.46, p = 0.026). No correlation between baseline MMN amplitude and change of depressive symptoms was observed in the sham group. CONCLUSION: Larger MMN amplitudes at baseline were associated with greater improvement in depressive symptoms only after active iTBS over the DMPFC. Indicating potential predictive properties of MMN in DMPFC iTBS in MDD, warranting replication in larger samples.
Anderson et al. (Sun,) studied this question.