Theory of mind in subjects with major depressive disorder: is it influenced by repetitive transcranial magnetic stimulation?

Objectives. To assess, in a sample of subjects with current major depressive disorder, whether high frequency repetitive transcranial magnetic stimulation (HF-rTMS) is able to influence affective "theory of mind" (ToM). Methods. We conducted a pilot naturalistic trial in which 14 subjects with MDD were treated with daily HF-rTMS over their left dorsolateral prefrontal cortex for 4 weeks. Objective depressive symptoms and affective ToM (as assessed, respectively, by the 21-item Hamilton Depression Rating Scale and the Reading the Mind in the Eyes Test [RMET]) were measured pre-post HF-rTMS treatment. Results. Our findings indicated the absence of a significant main effect for pre-post RMET scores, yet a significant interaction between pre-post RMET performance and change in depressive symptoms. Therefore, depressed subjects in our sample exhibited ToM improvements in proportion to their antidepressant response. Conclusions. We have shown that HF-rTMS is able to influence ToM in subjects with MDD. We hypothesize that this effect could be associated, at least in part, with clinical improvement over time. However, further studies with larger samples and controlled designs are needed to better clarify our preliminary findings.