Transcranial magnetic stimulation (TMS) is a non-invasive procedure that uses magnetic pulses to stimulate neurons and increase activity in the brain. When applied to areas of the brain that are important for mood regulation, the magnetic fields activate the neurons and relieve depression symptoms.
There are two approved types of TMS:
- Repetitive TMS (rTMS)
- Deep TMS.
The main difference is how deep the magnetic pulses penetrate the brain.
Repetitive transcranial magnetic stimulation (rTMS)
A TMS machine uses a figure 8-shaped coil which is placed near the scalp. The magnetic field generated by the coil passes through to the surface of the brain and generates electric currents in the local neurons as well as in any neural networks that may be connected to this area. The magnetic pulses reach up to 3cm beneath the skull. Activating the neurons in the prefrontal cortex of the brain, an area important for mood regulation, can relieve depression symptoms.
Deep transcranial magnetic stimulation (dTMS)
The second type of TMS device uses a different coil, named the H-coil. This coil also generates magnetic pulses which stimulate the neural networks but can penetrate up to 4 cm beneath the skull to reach deeper regions of the brain, such as the dorsolateral and ventrolateral prefrontal areas. These areas are important for mood regulation in depression, and their stimulation can impact other areas of the brain that may be important in depression.
How effective are the therapies?
Given rTMS was the first type of TMS to be approved it is no surprise that there have been more studies using rTMS in patients with depression. Clinical trials and real-world studies both demonstrate that rTMS is an effective treatment for people with depression. Since optimising the rTMS treatment regime, 58% of people with depression have been shown to respond to treatment and 37% enter remission.
The largest dTMS study, which was used to gain approval of the device, involved more than 200 patients with depression. In this study, 38% of patients responded to dTMS and 33% entered remission.
Comparison of rTMS and dTMS as a depression treatment
|Penetration beneath skull||Efficacy|
|rTMS||3cm||Extensively studied; up to 58% response and 37% remission in real world clinical practise|
|dTMS||4cm||Not as well studied; 38% response and 33% remission in clinical trial setting|
Are there any differences in safety?
Both rTMS and dTMS are safe, well-tolerated, non-invasive treatments. There does not appear to be any difference in the type or number of side effects.
- Australian depression treatment guidelines
- TMS a drug-free depression treatment
- How to treat severe depression
- Carpenter L et al. Transcranial magnetic stimulation (TMS) for major depression: a multisite, naturalistic, observations study of acute treatment outcomes in clinical practice. Depression and Anxiety 2012; 29: 587-596.
- George MS et al. Daily left prefrontal transcranial magnetic stimulation therapy for major depressive disorder. Arch Gen Psychiatry. 2010; 67: 507-516.
- Levkovitz Y et al. Deep transcranial magnetic stimulation over the prefrontal cortex: Evaluation of antidepressant and cognitive effects in depressive patients. Brain Stimulation 2009; 2: 188-200.
- Levkovitz Y et al. Efficacy and safety of deep transcranial magnetic stimulation for major depression: a prospective multicenter randomized controlled trial. World Psychiatry 2015; 14: 64-73.
- O’Reardon JP et al. Efficacy and safety of transcranial magnetic stimulation in the acute treatment of major depression: a multisite randomized controlled trial. Biol Psychiatry 2007; 62: 1208–1216.