In the 1700s, an Italian physician figured out how to perform an eerie parlor trick. Luigi Galvani hung frog legs from a metal railing. Then, atmospheric electricity energized the severed limbs, causing them to dance and kick.

These Frankenstein-like experiments did more than captivate an audience. Eventually, they helped scientists understand how electrical impulses power human nerve cells.

More than two centuries later, this understanding has led to the development of nondrug procedures that use the brain’s electrical impulses to treat formerly intractable psychiatric and neurologic conditions. One of these procedures, transcranial magnetic stimulation (TMS), was first approved by the Food and Drug Administration (FDA) in 2008 to treat depression. In the years since, the FDA cleared TMS for use in several other conditions, including migraine, obsessive-compulsive disorder (OCD) and tobacco addiction. Ongoing research may eventually lead to FDA approval for additional psychiatric and neurologic disorders.

What is TMS?

TMS uses magnetic fields to stimulate areas of the brain thought to be involved in depression, migraine, nicotine addiction or obsessive-compulsive disorder (OCD). Though all TMS devices use magnetic fields, the specifics of the procedure vary depending on the condition treated.

• Repetitive TMS (rTMS) is most often used to treat depression. It delivers magnetic waves in a series of pulses.
• Deep TMS (dTMS) delivers a series of pulses that reach deeper into the brain. This form of TMS can be used to treat OCD and nicotine addiction.
• Single-pulse TMS (sTMS) delivers one pulse. This handheld device is used to treat migraine.

TMS machines vary in size and shape. Some have a wand-like coil that is placed against the scalp, while others look more like helmets. The handheld sTMS device can be administered at home, whereas the dTMS and rTMS devices require the expertise of a healthcare professional.

What happens during a TMS treatment?

For rTMS or dTMS treatments, you’ll relax in a chair at your healthcare professional’s office or clinic.

Someone will place the TMS coil, wand or helmet against your scalp. The placement of the device will vary, depending on your condition.

Your healthcare professional will use the device to deliver one or more magnetic pulses. You might notice knocking, clicking or tapping against your head as the pulse or pulses are administered. The strength of the magnetic impulse is about the same as that of an MRI. In addition:

• Each session ranges from 3.5 minutes to 37 minutes, depending on the machine and the condition being treated.
• The procedure does not involve anesthesia or a sedative. You’ll remain fully awake.
• Side effects include temporary scalp discomfort, headache, tingling and lightheadedness. If side effects become intolerable, your healthcare professional can adjust the TMS device to reduce your symptoms.

The length of your treatment and the number of pulses will depend on the condition being treated.

Learn more: How transcranial magnetic stimulation works.

FDA-approved TMS treatments

 The FDA has approved the use of TMS for the following conditions:

• Treatment-resistant depression and anxiety with major depressive disorder.
• Migraine.
• Obsessive-compulsive disorder (OCD).
• Tobacco addiction.

TMS for major depression and anxious depression

One-third to half of people with depression don’t find relief from antidepressants. Because TMS works differently on the brain, it can sometimes bring relief when these other options have failed, helping roughly 60% of people to feel better within several weeks of treatment.

In research done in conjunction with Mayo Clinic, people with major depression who underwent five rTMS sessions a week for 4 to 6 weeks reported fewer depressive symptoms than study participants who were given a placebo treatment. About twice as many people who received TMS went into remission compared to people who were given placebo treatments.

“There are many theories about how TMS works for depression,” says Simon Kung, M.D., a professor of psychiatry at Mayo Clinic College of Medicine and Science. “Probably the best one is that there is a depression circuit in the brain, and we need to stimulate it to bring about mood changes.”

Though promising, rTMS doesn’t work for everyone and is not a long-lasting cure, says Dr. Kung.

There’s no way to know who will respond to rTMS and who will not, says Dr. Kung. However, he says, rTMS may be worth trying if you haven’t found relief from one or more antidepressants, Dr. Kung says.

This form of TMS may not be the best choice for people with depression who also have chronic headaches, as the tapping sensation from the rTMS magnet can worsen headache symptoms. Similarly, people with very severe depression usually find swifter relief from electroconvulsive therapy coupled with medication, says Dr. Kung. This includes people who are failing to thrive, losing weight from decreased appetite, experiencing slowed thoughts and movements, struggling with personal hygiene or basic self-care, and not getting out of bed much.

Given that headache is one of the side effects of rTMS, it might seem odd that the treatment is also approved for migraine, a neurological disorder that involves recurrent attacks of head pain coupled with other symptoms such as nausea, vomiting, and sensitivity to light and sound.

However, in this case, a different form of TMS is used.

Unlike the devices used for depression and other conditions, the sTMS device for migraine is much smaller, delivers fewer pulses and is placed against the back of the head instead of the front. It also can be used at home.

• To treat a migraine attack, you deliver one pulse that lasts less than one second.
• To prevent migraine, you use four pulses, twice a day, along with additional pulses, as needed, to treat migraine attacks.

In research done in part by Amaal J. Starling, M.D., at Mayo Clinic, 46% of study participants who used sTMS experienced more than a 50% reduction in their number of headache days.

Dr. Starling says she recommends the treatment for people who:

• Prefer a nondrug option for migraine treatment.
• Continue to experience migraine attacks after trying prescription medications.
• Cannot take prescription migraine medicines due to other medical conditions or medicines.

Learn more: How sTMS works for migraine headache relief.

TMS for obsessive-compulsive disorder (OCD)

People withobsessive-compulsive disorder (OCD) have unwanted thoughts and fears that lead them to perform repetitive (or compulsive) behaviors.

Current treatments for OCD include psychotherapy and medication. However, not everyone fully benefits from these options. TMS provides another tool when these traditional options aren’t effective.

Deep transcranial magnetic stimulation (dTMS) uses a powerful coil to deliver impulses deep into the brain. In research involving 99 people with OCD, participants who received six weeks of daily dTMS treatments experienced greater symptom relief compared to study participants who were given placebo treatments.

As with depression, TMS doesn’t work for everyone with OCD. In addition, for some people, several weeks of daily treatments involves more time than they are willing to devote to therapy. Cost also can be a factor. So, talk with your healthcare professional to make sure you understand all the pros and cons.

TMS for tobacco cessation

As many as 70% of tobacco users want to quit. However, few are successful, according to the Centers for Disease Control and Prevention (CDC). Nicotine replacement products, medication and therapy can support someone during the quitting process and help to improve their success. However, long-term success is only about 19% to 33%, even with these methods.

Approved by the FDA to treat tobacco addiction in 2020, TMS offers another option. In a study involving 115 people, those who underwent 13 dTMS sessions delivered over three weeks had a higher quit rate after treatment compared to study participants who received a placebo treatment.

Potential other uses

Research continues into other potential uses for TMS, including treating epilepsy, cognitive impairment, pain, tinnitus and more. Though some of this research is promising, it’s not yet robust enough to earn FDA approval.

Is TMS right for you?

If you have depression, migraine, OCD or tobacco addiction and you’ve already tried other treatment options, TMS may be worth exploring.

Talk to your healthcare professional about the benefits and risks.

Drawbacks to TMS treatment include cost and time commitment. Though sTMS treatments for migraine can be done at home, other TMS treatments involve visiting a healthcare professional five or more days a week for several weeks. In addition, a series of these office-based treatments also can cost $10,000 to $15,000. The at-home sTMS device used for migraine costs around $400 a month. Despite the FDA approval, some medical insurance companies don’t cover TMS. Others require you to try less expensive options first.