Frequently asked questions about TMS

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TMS stands for Transcranial magnetic Stimulation. It is a non-invasive procedure that uses magnetic fields to stimulate nerve cells in the brain to improve symptoms of depression and other mental health conditions (Simons).

TMS is a highly effective treatment for depression. Based on the largest clinical study of over 5,000 patients treated with TMS:

When self-evaluation is used to measure symptoms, 58-69% of patients show significant improvement, defined as at least a 50% reduction in depression symptoms, and 28-36% of patients achieve remission, meaning their depression symptoms become minimal or absent. 

When evaluated by clinicians rather than patient self-reports, success rates were even higher, with 69-83% of patients responding, and 47-63% of patients going into remission from depression.

These response rates are particularly impressive given that many patients trying TMS have already failed to respond to multiple antidepressant medications (Sackeim et al.).

A TMS machine uses electromagnetic induction to stimulate specific brain regions. Here's how it works:

1. The machine contains a large capacitor charged to about 2,000 volts that releases pulses of strong electrical current (around 7,000 amps) through a figure-8 shaped coil placed against your scalp.

2. When this current flows through the coil, it generates a powerful but brief magnetic field (about 2 Tesla - similar strength to an MRI machine) that passes painlessly through your skull.

3. This time-varying magnetic field induces a much smaller electrical field in the brain tissue beneath (about 1 volt per centimeter). When this electrical field reaches a certain threshold, it causes neurons in that specific brain region to fire.

4. Modern TMS machines use a figure-8 coil design that creates a more focused stimulation point where the two circles meet, allowing for precise targeting of specific brain regions.

The magnetic field can reach about 2-3 centimeters deep into the brain, making it possible to stimulate areas involved in mood regulation. The machine delivers these pulses in specific patterns during each treatment session to help normalize brain activity in depression.

Think of it like a highly targeted magnetic pulse that temporarily activates specific brain circuits - similar to how a conductor uses a baton to direct specific sections of an orchestra (Deng).

TMS therapy is very safe. The safety of TMS continues to be supported by meta-analyses of the published literature, and is an FDA-approved treatment for depression. It has been used for thousands of patients with minimal side effects.

TMS is FDA approved to treat Major Depressive Disorder, Obsessive Compulsive Disorder, and smoking cessation. There are many protocols that show strong efficacy and safety for treatment of Anxiety, PTSD, migraines, tinnitus, ADHD, chronic pain, post-stroke recovery and minor cognitive impairment. Lastly, TMS is currently being studied for its application to Parkinson's Disease, Dementia, and Bipolar Disorders I and II. The utilization of TMS is growing rapidly at this time, with new clinical trials being published every month.

Transcranial Magnetic Stimulation (TMS) works through several key mechanisms to treat depression:

At the brain circuit level, TMS delivers focused magnetic pulses to activate specific networks involved in mood regulation. The most common target is an area called the dorsolateral prefrontal cortex (DLPFC), which shows reduced activity in many people with depression. TMS helps normalize communication between this region and deeper brain areas like the anterior cingulate cortex that process emotions and motivation.

At the cellular level, repeated TMS sessions promote beneficial changes in how brain cells connect and communicate. This process, called neuroplasticity, involves strengthening some connections while weakening others. TMS also affects important brain chemicals like dopamine that influence mood. These changes help shift brain activity patterns away from depression and toward healthy emotional processing.

Unlike medications that affect the entire brain, TMS can precisely target specific circuits involved in depression. The effects build up gradually over multiple sessions and can long after treatment ends. This is because TMS creates lasting changes in how brain cells are wired together, rather than just temporarily altering brain chemistry.

Recent research shows TMS may also work by helping the brain escape from "stuck" patterns of activity associated with depression. By modulating key brain networks over several weeks of treatment, TMS allows a gradual return to more flexible and healthy brain function (Downar).

The following is a general list of contraindications for TMS, although it is up to the physician to evaluate each person's situation novelly in order to determine if TMS is right for them.

Metal Implants

The only absolute contraindication to TMS is the presence of metal implants in a person’s head, neck, or scalp. More specifically, there should be no ferromagnetic metals within a 30 cm radius of the treatment coil. Implants made of titanium are considered safe for TMS so long as they are not implanted directly on the treatment target (usually the left dorsolateral prefrontal cortex), or on the motor cortex spot C3, which is utilized during the Cortical Mapping. The magnetic field generated by the TMS pulse attracts ferromagnetic objects and repels non-ferromagnetic conducting objects, so there is potential for displacement or elevating the temperature of these materials if they are within 30 cm of the magnetic coil. However, a person with silver amalgam dental work (fillers, braces, retainers) is not disqualified from TMS. Moreover, because the most common metal used for implants is titanium, it is more common than not that patients with implants are still in the clear.

Seizure Disorders and Related

The risk of rTMS-induced seizures is extremely low. Even in groups of patients who are taking CNS-related medications, as long as traditional stimulation parameters and appropriate coils are used during treatment, the likelihood of epilepsy is minimal. However, for patients with: 1) a personal history of epilepsy (one or several seizures in the past in untreated patients), or patients who have received treatment; 2) cerebrovascular, traumatic, neoplastic, infectious, or metabolic lesions, even if no history of epilepsy and no use of anticonvulsants; 3) taking drugs that may lower the seizure threshold, but not taking anticonvulsants that may prevent seizures at the same time; 4) people with sleep deprivation and alcoholism need to consider the possibility of increased risk of seizure.

Deng, Z. D. (2020, April 28). Transcranial Magnetic Stimulation: Physics, Devices, and Modeling [Video]. National Institute of Mental Health. NIMH Non-invasive Neuromodulation Unit.

Downar, J., Siddiqi, S.H., Mitra, A., Williams, N., Liston, C. (2024). Mechanisms of Action of TMS in the Treatment of Depression. In: Browning, M., Cowen, P.J., Sharp, T. (eds) Emerging Neurobiology of Antidepressant Treatments. Current Topics in Behavioral Neurosciences, vol 66. Springer, Cham. https://doi.org/10.1007/7854_2024_483

George MS, Lisanby SH, Avery D, et al. Daily Left Prefrontal Transcranial Magnetic Stimulation Therapy for Major Depressive Disorder: A Sham-Controlled Randomized Trial. Arch Gen Psychiatry. 2010;67(5):507–516. doi:10.1001/archgenpsychiatry.2010.46

Harold A. Sackeim, Scott T. Aaronson, Linda L. Carpenter, Todd M. Hutton, Miriam Mina, Kenneth Pages, Sarah Verdoliva, W. Scott West, Clinical outcomes in a large registry of patients with major depressive disorder treated with Transcranial Magnetic Stimulation, Journal of Affective Disorders, Volume 277, 2020, Pages 65-74, ISSN 0165-0327, https://doi.org/10.1016/j.jad.2020.08.005.

Simons, W., & Dierick, M. (2005). Transcranial magnetic stimulation as a therapeutic tool in psychiatry. The World Journal of Biological Psychiatry, 6(1), 6–25. https://doi.org/10.1080/15622970510029812

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