The World Health Organization estimates depression affects 5% of the adult population and is the leading cause of disability and the 3rd cause of disease burden worldwide. Despite progress in therapies and pharmacology, 30% of patients have refractory symptoms. Patients with partial response and patients who do not want or are intolerant to medication can benefit from alternative treatment modalities such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS). However, there is scant literature comparing these two neuromodulatory techniques. The authors provide an overview of rTMS and tDCS to guide clinicians.

A review of MEDLINE, Google Scholar, and EBSCOHost databases was conducted. Keywords used included “rTMS,” “tDCS,” and “depression.” All types of articles discussing or comparing the modalities were selected. The unique characteristics, indications, and side effects of rTMS and tDCS were included.

rTMS is a neurostimulator used in-clinic that induces depolarization and neuronal activity in the dorsolateral prefrontal cortex, where hypofunction has historically been associated with depressive symptoms. The treatment is Food and Drug Administration (FDA) approved, and the most common protocol consists of 36 sessions over 8-9 weeks. Side effects are mild and temporary, and patients can resume daily activities after sessions. Its absolute contraindications are limited to metallic objects or implanted stimulator devices in or near the head. The total cost varies from $6,000-$11,000 but is covered by most insurance.

In contrast, tDCS is a cost-effective, small, and portable neuromodulator self-administered by patients at home that either increases or decreases intrinsic neural firing in the primary motor cortex and dorsolateral prefrontal cortex. Multi-session tDCS is thought to promote or regulate information processing efficiency. The most common protocol uses a constant low current for 20-30 minutes applied daily for 10 to 15 days. Common side effects are mild and temporary, and there is no absolute contraindication. Some meta-analyses have found its efficacy comparable to rTMS or antidepressants. However, due to uncertainties about the specific mode of administration, number of treatments, and duration of effect, its status remains investigational by the FDA.

The efficacy and safety of rTMS for the treatment of depression have been demonstrated in numerous studies. However, the lack of adequately equipped clinics and large cost limits its availability in spite of FDA approval. In contrast, tDCS has some advantages, including safety, tolerability, ease of administration at home, and cost-effectiveness, but requires further research and more rigorous evidence.

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