Cognitive outcomes of transcranial magnetic stimulation in treatment-resistant depression: a randomized controlled study

Major depressive disorder (MDD) is a significant cause of workforce loss, and is associated with cognitive impairments which can continue even after the elimination of mood and behavioural symptoms. The aim of this study was to investigate the benefit of transcranial magnetic stimulation (TMS) on cognitive functions in treatment resistant depression. This randomised controlled clinical trial was conducted at a university hospital, department of psychiatry (tertiary centre) between October 2019 and July 2020. The study included 30 patients with depressive disorder, aged 18-50 years, who did not respond to at least two antidepressant medications for at least 8 weeks (one drug used was serotonin norepinephrine reuptake inhibitor [SNRI]; and 15 healthy control subjects. The patients were separated into two equal groups in a double-blind, random manner, and 20 sessions of repeated TMS was applied to one group, and 20 sessions of sham TMS to the other. The Montgomery Asberg Depression Scale (MADRS), Hamilton Depression Rating Scale (HAM-D), Stroop test, Wisconsin Card Sorting Test (WCST), Digit Span Test (DST), Trail Making Test A-B, and Verbal Memory Processes Test (VMPT) were applied to the patients before and after the TMS procedure. The decrease in the HAM-D score was greater in the active magnetic stimulation (25 trains, 10 Hz, 110% motor threshold intensity) group, and with the exception of verbal memory processes, better performance was obtained by the active magnetic stimulation group than the sham group in the cognitive function tests. TMS was seen toimprove the cognitive defects present in the active phase of treatment-resistant depression, and therefore TMS could provide early improvement in cognitive functions in clinical use. Key words: Depression, transcranial magnetic stimulation, neurocognitive functi.