Dual Neuromodulation for Depression: Boosting TMS With tES

Brief Summary

Major depressive disorder (MDD) is a common and disabling condition. Transcranial magnetic stimulation (TMS) is an established non-invasive neuromodulation treatment for depression, but clinical response varies considerably between individuals. One possible reason for this variability is that the effects of TMS may depend on the pattern of ongoing brain activity at the time stimulation is delivered. This mechanistic, randomised, single-blind study will investigate whether synchronising TMS with transcranial alternating current stimulation (tACS), a form of weak electrical brain stimulation, can enhance the neurophysiological and cognitive effects of TMS in people experiencing a current moderate major depressive episode. The combined intervention is referred to as synchronised TMS (tsTMS). Up to 60 participants will be recruited and randomised in a 1:1:1 ratio to one of three groups: (1) TMS synchronised to the peak of a theta-frequency tACS waveform, (2) TMS synchronised to the trough of a theta-frequency tACS waveform, or (3) TMS combined with sham tACS. Participants will receive five daily neuromodulation sessions over one week. The primary objective is to estimate variability in change in emotional processing, measured using the Cambridge Cognition Emotional Bias Task, in order to inform the design and sample size calculation of a future clinical trial. The study will also assess participant acceptability and tolerability of the intervention. Secondary objectives include exploring changes in brain oscillatory activity measured using electroencephalography (EEG), cognitive performance, mood and anxiety symptoms, functional outcomes, and digital biomarkers collected from an optional wearable device. This study is designed to investigate mechanisms and feasibility rather than provide a full therapeutic course of TMS. Findings will be used to inform the development of a future definitive clinical trial evaluating whether synchronised neuromodulation can improve outcomes in depression.