Cognitive outcomes of TMS treatment in bipolar depression: Safety data from a randomized controlled trial

Background: Bipolar depression (BD) is a highly prevalent condition associated with marked cognitive deficits that persist even in the euthymic phase of the illness. Pharmacological treatments for BD might further aggravate cognitive impairment, highlighting the need of developing interventions that present cognitive safety. In this study, we evaluated the cognitive effects of H1-coil (deep) transcranial magnetic stimulation (TMS) in patients with treatment-resistant bipolar depression. Methods: Fourty-three patients were randomized to receive 20 sessions of active (55 trains, 18 Hz, 120% resting motor threshold intensity) or sham rTMS within a double-blind, sham-controlled trial. A battery of 20 neuropsychological assessments, grouped in 6 domains (attention and processing speed, working memory and executive function, inhibitory control, language, immediate verbal memory, and long-term verbal memory) was performed at baseline and after 4 and 8 weeks of trial onset. Depressive symptoms were assessed with the 17 item Hamilton Rating Scale for Depression. Results: Cognitive improvement was shown for all cognitive domains. It occurred regardless of intervention group and depression improvement. For the language domain, greater improvement was observed in the sham group over time. No correlations between depression (at baseline or during treatment) and cognitive improvement were found. Limitations: Absence of healthy control group. Conclusion: The results of this exploratory study provide evidence on the cognitive safety of H1-coil TMS for BD patients. Putative pro-cognitive effects of rTMS in BD were not observed and thus should be further investigated.