Transcranial magnetic stimulation (TMS) is a noninvasive brain stimulation treatment that uses magnetic pulses to activate nerve cells in targeted areas of the brain. It’s most commonly used for depression that hasn’t responded to medication, though it’s also cleared for obsessive-compulsive disorder, migraines, and smoking cessation. The procedure requires no anesthesia, no surgery, and no sedation.
How TMS Works
A TMS device generates a brief, powerful magnetic field through a coil placed against your scalp. Unlike electrical stimulation, which has to push current through skin and bone, the magnetic field passes through those tissues without being weakened. Once it reaches the brain, it induces a small electrical current in the underlying nerve tissue. That current is strong enough to trigger neurons to fire, essentially jump-starting activity in brain regions that may be underactive.
The magnetic pulse interacts directly with the insulated fibers (axons) that connect neurons to each other. When the pulse hits these fibers, it causes them to depolarize, the same process that happens naturally when a nerve cell sends a signal. A single pulse can trigger a chain of neural activity in the targeted area. By delivering pulses repeatedly over multiple sessions, TMS can produce lasting changes in how those brain circuits function.
What Happens During a Session
You sit in a reclined chair, fully awake and alert. A technician places a magnetic coil against a specific spot on your head. Before your first treatment session begins in earnest, the clinician needs to calibrate the machine to your brain. They do this by finding your “motor threshold,” which is the minimum amount of magnetic energy needed to make your thumb or index finger twitch. The coil is moved in small increments across the scalp, starting near the top of the head, until the spot that produces the most reliable finger movement is identified. The clinician then dials the intensity up and down to find the lowest power setting that causes a visible twitch at least half the time. This number becomes the baseline for your treatment intensity.
Once calibrated, the coil is repositioned over the treatment target, typically an area of the prefrontal cortex involved in mood regulation. During the session, you’ll hear a repetitive clicking sound and feel a tapping or knocking sensation on your scalp. Some people find the tapping mildly uncomfortable at first, but most adjust to it quickly. You can talk to the clinician throughout, and you’re able to drive yourself home afterward.
Types of TMS Devices
Not all TMS systems work the same way. The differences come down to coil design, pulse patterns, and how deep the magnetic field reaches into the brain.
- Repetitive TMS (rTMS) uses a figure-8 shaped coil that delivers focused stimulation to a relatively shallow depth, roughly 1 to 1.5 centimeters below the skull. Because the field is concentrated in a small area, precise coil placement matters. Sessions tend to be longer.
- Deep TMS (dTMS) uses a helmet-like device containing an H-coil that generates a broader magnetic field reaching 3 to 4 centimeters deep. This allows it to stimulate structures deeper in the brain’s mood circuitry, including regions that standard rTMS can’t easily reach. Coil positioning is less sensitive because the field covers a wider area.
- Theta-burst stimulation (TBS) delivers pulses in a pattern that mimics the brain’s natural rhythms. It can achieve similar effects in a fraction of the time. Some theta-burst protocols complete a session in under 10 minutes, compared to 20 to 40 minutes for conventional rTMS. In 2025, the FDA cleared an accelerated deep TMS protocol for major depressive disorder.
Conditions TMS Treats
The FDA has cleared TMS for four conditions: major depressive disorder (including treatment-resistant depression), obsessive-compulsive disorder, migraines with aura, and smoking cessation. Depression is by far the most common use. TMS is typically offered when at least one round of antidepressant medication hasn’t worked or when side effects from medication are intolerable.
For depression, the results can be significant. In a study of 247 patients with treatment-resistant depression, 30 sessions of deep TMS produced a response rate near 80% and a full remission rate above 60% on the most commonly used rating scale. Even after 20 sessions, roughly 69% of patients showed a meaningful response. Physician-rated outcomes were even stronger, with remission rates reaching 78% after a full course. These numbers are notable because treatment-resistant depression, by definition, means other therapies have already failed.
Side Effects and Safety
The most common side effects are mild: headache, slight scalp discomfort at the stimulation site, and tingling or twitching of facial muscles during the session. These tend to decrease over the course of treatment as you get used to the sensation.
The most serious risk is seizure, but the likelihood is extremely low. A review of over 318,000 TMS sessions found 24 seizures total, putting the rate at roughly one per 60,000 sessions. Across all device types, the overall seizure risk is well under 1%. Certain factors can increase that small risk, including alcohol use, sleep deprivation, brain injury, and a personal or family history of seizures. Your provider will screen for these before starting treatment.
Who Should Not Get TMS
TMS is not safe for anyone who has metal implants in or near the head. This includes cochlear implants, aneurysm clips, stents, deep brain stimulators, bullet fragments, or any other conductive or magnetic metal within about 30 centimeters of where the coil will be placed. The strong magnetic field can interact with these objects and cause serious injury. Implanted stimulators of any kind near the head, whether active or inactive, are also a strict contraindication.
Cardiac pacemakers, implantable defibrillators, and vagus nerve stimulators also require caution. Pregnancy, a history of seizures, brain tumors, and certain psychiatric conditions like psychotic disorders may affect eligibility depending on the clinical situation.
Insurance Coverage and Cost
Medicare and many private insurers cover TMS for severe major depressive disorder, but the requirements are specific. Under current Medicare guidelines, you need a confirmed diagnosis of severe depression and must have failed at least one adequate trial of antidepressant medication, or demonstrated that you can’t tolerate medication due to side effects. Coverage typically extends for up to six weeks of treatment.
If you’re pursuing TMS for OCD, migraines, or smoking cessation, coverage is less predictable and varies widely by insurer. Out-of-pocket costs for a full treatment course without insurance can range from several thousand dollars upward, so verifying your benefits before starting is worth the phone call.