Safety and Efficacy of Continuous Theta Burst “Intensive” Stimulation in Acute-Phase Bipolar Depression

Repetitive transcranial magnetic stimulation efficacy in unipolar depression is known, but its efficacy in acute-phase bipolar depression is at best modest. Citing differential right dorsolateral prefrontal cortex hyperconnectivity implicated in BD, we aimed to study the effect of novel continuous theta burst stimulation (cTBS) targeting right dorsolateral prefrontal cortex in a randomized rater blinded placebo control design.Nineteen patients aged 18 to 59 years (baseline Hamilton Depression Rating Scale [HAM-D] 17 severity score >18) were randomly allocated to active cTBS (n = 11) and sham cTBS (n = 9) groups using block randomization method. They received 15 cTBS sessions (burst of 3 pulses delivered at 50 Hz, repeated every 200 ms at 5 Hz, 600 pulses per session), 3 sessions per day (total of 1800 pulses) for 5 days in a week at 80% resting motor threshold. The HAM-D, Beck Depression Inventory, Hamilton Anxiety Rating Scale, World Health Organization's abbreviated quality of life assessment, and Changes in Sexual Functioning Questionnaire were assessed at baseline, after the last session, and at 2 weeks after repetitive transcranial magnetic stimulation. Intention-to-treat analysis was conducted and missing values (2 patients) were replaced using the last observation carried forward method.On repeated measures analysis of variance, a significant within-group time effect (from pretreatment to 2 weeks after TBS) for HAM-D ( F = 15.091, P < 0.001), Beck Depression Inventory ( F = 22.376, P < 0.001), Hamilton Anxiety Rating Scale ( F = 18.290, P < 0.001), Changes in Sexual Functioning Questionnaire ( F = 9.281, P = 0.001), and World Health Organization's abbreviated quality of life assessment ( F = 24.008, P < 0.001). The integrity of the blind assessed by the guess matrix was good. When significant between group*time effect was compared, none of the variables retained statistical significance. No major adverse effects were reported, and none of the patients discontinued the trial because of adverse effects.Our trial concludes that although safe and well tolerated, the therapeutic efficacy of intensive intermittent TBS in acute-phase bipolar depression is inconclusive. Choice of lower total number to sessions and smaller intersession interval along with small sample size limit the study findings.