What Is TMS Therapy? How It Works and Who It Can Help

If you’ve tried two or three antidepressants and still feel stuck, the words “brain stimulation” can sound like a last resort. Transcranial magnetic stimulation, or TMS, usually isn’t one, and it’s gentler than many people expect.

Your brain already runs on electrical signals. NIMH’s brain stimulation overview explains that a TMS coil switches a magnetic field on and off very rapidly, inducing weak electrical currents that stimulate the neurons beneath it. The pulses are aimed with precision at one brain site, usually the left prefrontal cortex for depression, instead of acting on your whole body.

For most people, depression treatment starts with antidepressants, talk therapy, or both, and the evidence behind medication is solid. A 2018 meta-analysis of 522 trials with more than 116,000 participants found that all 21 antidepressants studied worked better than placebo. The results are real, and the science is well established.

But many people try medication after medication without anyone explaining what else exists, and at Siggy we don’t think you should have to find the next option on your own.

TMS is one of those options: a noninvasive treatment that uses focused magnetic pulses to change activity in brain circuits tied to mood, cleared by the FDA for adults whose depression hasn’t improved after at least one antidepressant. It treats the same illness as your medication through a different route, a physical stimulus to one region instead of a drug that circulates through your body. The difference has nothing to do with marketing and everything to do with anatomy.

What This Page Covers

• How Does TMS Therapy Work?
• What Is TMS FDA-Cleared to Treat?
• What Happens During a TMS Session?
• How Well Does TMS Work for Depression?
• What Are the Side Effects and Risks of TMS?
• Who Is a Good Candidate for TMS?
• Talk Through Where You Are in Treatment

How Does TMS Therapy Work?

TMS relies on electromagnetic induction, the same physics that lets a changing magnetic field create a current in a wire. NIMH describes the field as about as strong as an MRI scanner’s. Because the pulses pass easily through the skull, they reach nerve cells without surgery or implanted electrodes.

For depression, the coil usually sits over the left prefrontal cortex, an area NIMH describes as thought to be involved in mood regulation and cognitive control. A single pulse doesn’t treat depression. The effect builds through repeated stimulation, which is why TMS is given as a series of sessions. NIMH also notes that experts haven’t settled on the best coil position or pulse pattern, and research on targets and lasting improvement continues.

What Is TMS FDA-Cleared to Treat?

Most TMS devices are FDA-cleared rather than FDA-approved. The NIMH overview explains that clearance means a device is substantially equivalent to one the FDA already authorized, and it’s usually given to lower-risk devices used outside the body.

According to NIMH, TMS is cleared for:

• Depression that hasn’t improved with at least one antidepressant in the current episode, first cleared in 2008
• Obsessive-compulsive disorder
• Migraine
• Depression with anxiety
• Smoking dependence
• Add-on treatment of depression in adolescents 15 and older, cleared in March 2024

The OCD clearance came in 2018. In the trial behind it, the FDA’s 2018 announcement reported that 38% of patients responded to the active device compared with 11% on a sham device. Our guides to how OCD is treated and TMS for anxiety go deeper on those uses. Uses outside this list are still being researched and would be off-label.

What Happens During a TMS Session?

Your first appointment is usually the longest. The VA’s TMS program describes how a physician sends a few brief pulses over the left side of your head to find your motor threshold, the lowest power that makes your thumb twitch, and uses it to set your dose. The coil then moves over the dorsolateral prefrontal cortex, an area about the size of a golf ball toward the front of the brain.

After that, sessions are routine. You remove metal items like jewelry and hearing aids, sit in a chair fully awake, and wear earplugs because each pulse makes a loud click. You’ll feel a strong tapping on your scalp. There’s no sedation and no recovery time, so you can drive yourself home and go back to your day.

How Long Does a TMS Course Take?

The VA program notes that a typical course includes at least 30 treatments of 3 to 40 minutes each, spread over 1 week to 6 to 8 weeks depending on how many sessions you get per day. The three protocols you’re most likely to hear about differ mainly in timing.

Protocol	Session Length	Typical Schedule	Main Trade-Off
Standard rTMS (10 Hz)	About 37.5 minutes	5 days a week, 4 to 6 weeks	Longest individual sessions
Intermittent theta burst (iTBS)	About 3 minutes	5 days a week, 4 to 6 weeks	Rated slightly more painful
Accelerated iTBS (SAINT)	10 minutes, 10 times a day	5 days	Small studies, 4-week follow-up

The first two rows come from the THREE-D trial, which randomized 414 adults with treatment-resistant depression and found 3-minute theta burst sessions no less effective than 37.5-minute sessions, with similar dropout rates and side effects. The SAINT row comes from the FDA’s clearance summary, which describes MRI-guided targeting and reports remission in 11 of 14 people (78.6%) on active treatment versus 2 of 15 (13.3%) on sham. It also notes that the 70 patients in its four supporting studies came from a single site and that effectiveness wasn’t established beyond 4 weeks.

Before you book, our guides to TMS insurance coverage and TMS costs explain what plans typically ask for.

How Well Does TMS Work for Depression?

TMS helps a meaningful share of people whose depression hasn’t responded to medication, though it doesn’t help everyone.

A 2007 multisite trial randomized 301 medication-free adults who hadn’t benefited from prior treatment to active or sham TMS. Response rates were significantly higher with active TMS at weeks 4 and 6, remission was about twice as common by week 6, and only 4.5% stopped because of side effects. The main result did need a statistical adjustment for baseline differences between groups.

Real-world results look similar. A 42-practice study followed 307 outpatients who had tried an average of 2.5 adequate antidepressant treatments in their current episode. Clinicians rated 58% as responders and 37.1% as in remission, while patients’ own questionnaires showed response rates of 41.5% to 56.4%.

A 2019 BMJ meta-analysis pooled 113 trials with 6,750 patients. Standard high-frequency TMS over the left side roughly tripled the odds of response compared with sham, and theta burst performed about the same. Two forms of ECT were associated with higher response than other active treatments, and our guide to ECT explains its trade-offs.

Benefits often hold up. In a one-year follow-up of 257 patients, 62.5% of those who responded to an initial course still met response criteria across 12 months while continuing antidepressants, and 36.2% had TMS reintroduced at some point.

The CANMAT 2023 guidelines rate high-frequency TMS over the left prefrontal cortex as a first-line TMS protocol and say that, outside emergencies, TMS should generally be considered before ECT because it’s less invasive and people can keep working or attending school. They also note that remission is less likely with more severe symptoms and more previous antidepressant failures. Our deeper look at whether TMS works compares these numbers with switching medications.

What Are the Side Effects and Risks of TMS?

Most side effects are mild and short-lived. The VA program reports headaches in about half of patients and painful scalp sensations or facial twitching in about a third, and both tend to fade as treatment continues. Earplugs are required, and the VA notes no evidence of permanent hearing changes when they’re worn.

Seizure is the most serious risk, and it’s rare. A 2021 seizure survey of Clinical TMS Society members counted 18 seizures across 586,656 sessions and 25,526 patients, about 0.31 per 10,000 sessions or 0.71 per 1,000 patients. The FDA’s OCD announcement asks people with a history of seizures to discuss it with their provider first, and NIMH notes that long-term side effects haven’t been determined.

Who Is a Good Candidate for TMS?

TMS is cleared for adults with major depression that hasn’t improved enough after at least one antidepressant in the current episode, and since 2024 for adolescents 15 and older as an add-on treatment. Practical fit matters too, because a standard course means weekday visits for several weeks.

TMS isn’t right for everyone:

• The VA rules it out for non-removable metal in the head, other than braces or dental fillings, because the metal could heat up, move, or malfunction.
• The FDA’s OCD announcement lists metal objects and implanted devices in or near the head as contraindications, including cochlear implants, deep brain or vagus nerve stimulators, aneurysm clips or coils, stents, and bullet fragments.
• A history of seizures needs careful discussion first.
• When depression needs a rapid response, such as when someone is suicidal, catatonic, or not eating, NIMH describes ECT as an option.

If you’re weighing next steps, our overview of treatment-resistant depression options compares TMS with esketamine, ECT, and medication strategies, and our guide to ketamine for depression covers another newer approach.

If you’re having thoughts of suicide or feel unsafe, call or text 988. In an emergency, call 911. This article is for education only and isn’t a substitute for personal medical advice. It reflects sources available as of October 2026.

Talk Through Where You Are in Treatment

TMS is easiest to plan for when you have a clear record of what you’ve already tried, at what dose, and for how long. Our guide to TMS for treatment-resistant depression explains how candidacy is judged. If it feels like no one has checked in to see whether your treatment is actually working, start your anonymous intake with Siggy. It’s free, asks for no name or email, and lets you describe your symptoms and medication history in your own words. If medication is part of your plan, a licensed prescriber reviews your full history before anything is prescribed. Siggy doesn’t provide TMS, but you get a downloadable summary you can share with any clinician, including a TMS team, so you don’t have to retell your story from scratch.