Technical Report: Efficacy and Safety of Low-Intensity Transcranial Magnetic Stimulation in the Remission of Depressive Symptoms in Patients With Treatment-Resistant Depression in Mexico

Abstract

Transcranial magnetic stimulation (TMS) is a non-invasive neuromodulation technique that induces action potentials in the stimulated cortical area and has been approved by the Food and Drug Administration (FDA) for the treatment of major depressive disorder (MDD). The prevalence of MDD in Mexico almost tripled after the COVID-19 pandemic. In this study, we evaluated the safety and therapeutic effects of low-intensity TMS (Li-TMS) - characterized by inducing electric currents below the action potential threshold on the cerebral cortex - in 41 subjects diagnosed with treatment-resistant depression (TRD). A Li-TMS device dispensed repetitive magnetic pulses at 30 mT for 60 minutes during 20 sessions (once daily from Monday to Saturday) with the theta burst pattern. Our results suggest that Li-TMS is a safe therapy with antidepressant effects, demonstrated by the decrease in Beck Depression Inventory (BDI) scores and lessening of depressive symptoms.

Keywords: low intensity tms; major depression disorder; noninvasive neuromodulation; transcranial magnetic stimulation (tms); treatment-resistant depression (trd).

Figure 1. Correlation and distribution of BDI scores at different times of assessment throughout the Li-TMS treatment in patients with TRD.

The box plot depicts how the medians and interquartile ranges (IQRs) of the BDI scores decrease in each successive assessment. T1 (BDI assessment before session 1) reflects the highest IQR values in comparison with T2 (BDI assessment at the end of session 10) and T3 (BDI assessment at the end of session 20), which show lower IQR values, with T3 the lowest, suggesting that the Li-TMS treatment applied to TRD patients tends to decrease depressive symptoms over time.