The effects of repetitive transcranial magnetic stimulation on cognitive performance in treatment-resistant depression. A systematic review

BACKGROUND: Major depressive disorder (MDD) is a disabling illness associated with significant functional and psychosocial impairment. Although many psychopharmacological agents are currently available for its treatment, many MDD patients suffer from treatment-resistant depression (TRD). METHODS: A systematic review of the current literature (Pubmed/Medline, Scopus and ScienceDirect search) has been conducted with the primary aim to investigate the role of repetitive transcranial magnetic stimulation (rTMS) in improving neurocognition in patients with TRD. Studies were included according to the following criteria: (a) being an original paper in a peer-reviewed journal and (b) having analyzed the effect of rTMS on neurocognitive functioning in TRD. RESULTS: The combined search strategy yielded a total of 91 articles, of which, after a complete analysis, 22 fulfilled our inclusion criteria. Based on the main findings, most of the selected studies suggested the existence of a trend towards improvements in the neurocognitive profile using rTMS. Negative findings have also been reported. However, most studies were limited by their small sample size or included mixed samples, or the adopted single-blind designs potentially biased the blinding of the study design. CONCLUSION: rTMS is a noninvasive brain stimulation that may be considered a valuable and promising technique for cognitive enhancement in TRD.