What Is TMS? An Introduction to Transcranial Magnetic Stimulation & Neuromodulation

TMS & Neuromodulation · Part 1
Anton Ostashko, MD·Last medically reviewed July 10, 2026

Overview

Transcranial magnetic stimulation (TMS) is a non-surgical form of neuromodulation. A treatment coil placed against the scalp produces a rapidly changing magnetic field, which induces a small electric field in the underlying cerebral cortex. When pulses are delivered in a planned pattern over repeated sessions, TMS can influence the activity of brain circuits involved in mood, behavior, pain processing, and other functions.12

During routine therapeutic TMS, the patient remains awake. There is no incision, implanted device, general anesthesia, or sedation. Most people can return to usual activities after a session. The pulses are often described as tapping or knocking on the scalp; treatment is well tolerated by many patients, but it is not literally painless for everyone. Scalp discomfort and headache are among the most common adverse effects.1617

TMS has its longest and strongest clinical track record in major depressive disorder. In the United States, specific devices and protocols also have FDA-authorized indications for adult obsessive-compulsive disorder, short-term smoking cessation, anxiety symptoms that occur with major depression, adolescent depression in patients ages 15 through 21, migraine, and—since June 2026—adjunctive treatment of adult post-traumatic stress disorder (PTSD) with the device-specific MeRT system. These authorizations are device-, coil-, age-, target-, and protocol-specific; they do not mean that every TMS machine is cleared for every condition.101113141518

The most important TMS developments as of July 10, 2026 are:

  • Faster treatment formats are now part of mainstream clinical TMS. Intermittent theta-burst stimulation (iTBS) can deliver a treatment session in approximately 3 minutes on certain cleared systems, compared with roughly 20 to 40 minutes for many conventional protocols. A large randomized trial found once-daily iTBS noninferior to standard high-frequency rTMS for depression.34
  • Accelerated TMS now includes more than one FDA-cleared platform. The MRI- and functional-connectivity-guided SAINT system delivers a high-dose iTBS protocol condensed into 5 days. In May 2026, the FDA also cleared a MagVenture labeling expansion that permits multiple daily rTMS or iTBS sessions for eligible adults with major depression, including those who may have comorbid anxiety symptoms. Accelerated TMS is not one interchangeable recipe: pulse dose, target, intensity, number of sessions, and spacing between sessions all matter.67
  • A 2026 randomized study replicated benefit from the specialized 5-day SNT protocol. Among 48 randomized adults with treatment-resistant depression, 1-month remission occurred in 50.0% after active treatment and 20.8% after sham treatment. This is encouraging, but it was still a relatively small trial of a high-dose, specialized protocol and should not be generalized to every form of TMS.8
  • Personalized functional-connectivity targeting gained direct randomized support. In a June 2026 trial of 40 adults receiving high-dose accelerated TMS, individualized connectivity-based targets produced a larger median reduction in depression scores than Beam F3 scalp targeting. The study supports precision targeting in that specific setting, but it does not prove that every MRI-guided course is superior to every standard, scalp-targeted protocol.9
  • Adolescent access has expanded, but the indication is specific. Certain systems are cleared as an adjunct for major depressive disorder in patients ages 15 through 21. That does not create a universal pediatric indication for all devices, protocols, or diagnoses.10
  • Safety language should remain precise. Routine therapeutic TMS does not intentionally induce a seizure and generally has little risk of clinically significant cognitive impairment, but seizure is a rare possible adverse event. Hearing protection, implant screening, medication and substance review, and monitoring for mood activation are important parts of safe treatment.1617

Evidence cutoff: This article reflects publicly available evidence and U.S. regulatory information through July 10, 2026. FDA labeling is specific to the named device and protocol and can change over time.

What Does TMS Actually Do?

The word transcranial means across the skull. TMS works through electromagnetic induction: electrical current passes through a wire coil, creating a rapidly changing magnetic field. That magnetic field crosses the scalp and skull and induces an electric field in nearby cortical tissue. If the induced field is strong enough and oriented appropriately, it can activate axons and alter the activity of local neurons and the larger network to which they belong.17

A familiar demonstration is stimulation of the motor cortex. A single pulse over the hand area can produce a small thumb or finger movement. Clinicians use this response to estimate the patient’s motor threshold, which helps set treatment intensity. Motor threshold is a way to individualize the stimulation dose; it does not, by itself, identify the best prefrontal treatment target.

Therapeutic benefit does not come from a magnet simply “turning on” one brain spot. Repeated stimulation influences connected networks, and its effects depend on the target, pulse pattern, intensity, total dose, treatment schedule, the patient’s brain state, and the condition being treated. Traditional shorthand sometimes labels high-frequency stimulation as excitatory and low-frequency stimulation as inhibitory, but real human network effects are more complex and variable than that simple rule suggests.2

Single Pulses, Repetitive TMS, and Theta-Burst Stimulation

TermWhat it meansPractical significance
Single-pulse TMS (sTMS)One pulse, or a small number of separated pulsesUsed in neurophysiology and in a distinct portable prescription migraine device; it is not the same as an office-based depression course.15
Repetitive TMS (rTMS)Pulses delivered in repeated trainsThe broad category that includes many established depression and OCD protocols.
Intermittent theta-burst stimulation (iTBS)Short bursts of high-frequency pulses delivered in a theta-patterned sequenceSome cleared depression sessions last about 3 minutes; once-daily iTBS has evidence of noninferiority to conventional 10-Hz rTMS.34
Deep TMSA commercial term for systems using specialized H-coils that expose a broader and somewhat deeper cortical volumeIt is generally less focal than a figure-of-eight coil and does not mean DBS-like, pinpoint stimulation of a deep brain nucleus. FDA’s device classification describes direct stimulation of cerebral cortex, not magnetic focusing outside the cortex.11
Accelerated TMSMore than one treatment session per dayCan shorten a course from weeks to days for certain cleared protocols. The number of sessions, intersession interval, pulse dose, and targeting method are integral parts of the protocol.67

What Is Neuromodulation?

Neuromodulation is the deliberate alteration of nervous-system activity to improve symptoms. The term includes treatments that use magnetic fields, electrical current, implanted electrodes, or stimulation of peripheral nerves. It describes a broad family rather than a single technology.

  • TMS induces current in the cortex using a magnetic field and ordinarily requires no surgery or anesthesia.
  • Transcranial electrical stimulation, such as tDCS or tACS, applies weak current through scalp electrodes. Many psychiatric uses remain investigational, and consumer devices should not be assumed equivalent to prescription clinical TMS.
  • Electroconvulsive therapy (ECT) uses electrical stimulation under general anesthesia to intentionally produce a therapeutic seizure. It is non-surgical but is clinically and physiologically distinct from TMS.17
  • Vagus nerve stimulation and deep brain stimulation use implanted hardware and require a procedure or surgery.

A medication and a neuromodulation treatment are not opposites. Both ultimately change neural signaling, but they do so through different routes. TMS is often used alongside medication, psychotherapy, behavioral treatment, sleep care, rehabilitation, or other condition-specific treatment rather than replacing all other care.

What Is TMS FDA-Authorized to Treat?

U.S. regulatory language requires care. Most current TMS systems reached the market through 510(k) clearance, meaning the FDA found the device substantially equivalent to an appropriate legally marketed device for the stated use. The first device category for adult OCD entered through a De Novo authorization. “FDA-authorized” is a useful umbrella term, but the exact label must still be checked for the device being offered.1117

U.S. indicationWhat patients should understand
Major depressive disorder in adultsThe first U.S. TMS depression system was cleared in 2008 for adults who had not achieved satisfactory improvement from prior antidepressant treatment in the current episode. Multiple systems and conventional, iTBS, and accelerated protocols now have specific labeling.1467
Adolescent major depressive disorderSpecific systems are cleared as adjunctive treatment for patients ages 15 through 21. The age range and “adjunct” wording matter; this is not a blanket clearance for all children, diagnoses, or machines.10
Obsessive-compulsive disorderSpecific systems are authorized as an adjunct for adults with OCD. The protocol, H-coil, target, and symptom provocation procedure used in pivotal studies differ from standard depression TMS.1112
Depression with comorbid anxiety symptomsSome systems are labeled to treat depressive episodes and decrease anxiety symptoms in adults with major depression who also exhibit anxiety symptoms. This is not the same as a general FDA clearance for primary generalized anxiety disorder.14
Short-term smoking cessationA specific deep-TMS system is cleared as an aid in short-term smoking cessation for adults. It should be understood as part of a smoking-cessation plan, not a guarantee of abstinence.13
MigraineA portable, prescription single-pulse TMS device is cleared for acute and preventive treatment of migraine in adolescents age 12 and older and adults. This is a different device and dosing model from office-based repetitive TMS for depression.15
Post-traumatic stress disorderAs of June 2026, the MeRT system is cleared as an adjunct for adults with PTSD. It uses resting EEG/ECG to derive an individualized 8–13-Hz treatment frequency with compatible TMS hardware. The pivotal trial tested the complete system and did not isolate the independent contribution of frequency personalization.18

Other applications may be offered off label or studied in clinical trials. Off-label care can be medically appropriate, but it should be described honestly. The clinic should explain the evidence, alternatives, uncertainty, cost, and why a specific target and protocol are being recommended rather than implying that an FDA clearance for one condition proves effectiveness for another.

What Is a TMS Appointment Like?

1. Evaluation and Safety Screening

A responsible TMS program begins by confirming the diagnosis, severity, prior treatments, goals, and whether another treatment is more urgent or appropriate. The team reviews seizure history, fainting or unexplained episodes, neurological disease, bipolar-spectrum symptoms, medications and supplements, alcohol or sedative withdrawal risk, sleep deprivation, pregnancy when relevant, and implanted or retained metal and electronic devices.

2. Motor Threshold and Dose Calibration

The coil is positioned over motor cortex and stimulation is adjusted until a small hand-muscle response is detected, either visibly or with electromyography. Treatment intensity is then prescribed as a percentage of that individual motor threshold. Threshold may be rechecked when clinically indicated, including after meaningful medication or health changes.

3. Target Location

The therapeutic target may be located with scalp measurements, a validated method such as Beam F3, structural-MRI neuronavigation, or a specialized functional-connectivity workflow. The target used for depression is commonly within the dorsolateral prefrontal cortex; OCD and other protocols use different coils and targets.

4. The Treatment Session

The patient sits in a treatment chair while the coil is held against the scalp. Ear protection is used because each pulse produces a loud click. The patient usually feels tapping, pressure, tingling, or contraction of scalp or facial muscles. Intensity can often be increased gradually during early sessions to improve tolerability.

Session duration depends on the exact protocol. Certain iTBS sessions last about 3 minutes, while many conventional rTMS sessions last 20 to 40 minutes. Accelerated protocols deliver multiple sessions in a day with prescribed intervals between them. “Faster” does not mean that sessions can simply be stacked without respecting the cleared or evidence-based schedule.4717

5. A Course, Not Usually a One-Time Procedure

Many standard depression courses are delivered five days per week for approximately four to six weeks, sometimes followed by a taper. Accelerated protocols may condense treatment into several days or use several sessions per day over a longer interval. Maintenance or retreatment can be considered for selected patients, but there is no single universally established maintenance schedule.217

Symptoms should be measured at baseline and during treatment with standardized scales and functional goals. A course should not be judged only by how the patient feels on one day. Medication and psychotherapy are usually continued unless the treating clinicians make a deliberate change.

How Effective Is TMS?

There is no single honest “TMS success rate.” Outcomes vary with diagnosis, illness severity and duration, treatment resistance, comorbidity, target, coil, pulse pattern, dose, adherence, outcome definition, and follow-up time. Marketing figures drawn from one highly selected protocol should not be applied to every patient or device.

For depression, the 2025 consensus review endorsed by the National Network of Depression Centers, Clinical TMS Society, and International Federation of Clinical Neurophysiology concluded that rTMS has broad evidence for safety and efficacy. It also recognized once-daily iTBS as noninferior to standard rTMS and described accelerated and MRI-guided approaches as promising areas of continued development.2

The rapid SNT literature, commercialized in the FDA-cleared SAINT system, is an example of why the protocol must be named. The original double-blind randomized study and a 2026 randomized replication support a specialized, high-dose, connectivity-guided five-day treatment for adults with treatment-resistant depression. The 2026 study reported 1-month remission in 50.0% of active-treatment participants versus 20.8% with sham, but only 48 participants were randomized. Larger independent studies, longer follow-up, comparative trials, access data, and cost-effectiveness evidence remain important.58

Practical expectation: TMS can produce substantial improvement or remission in some patients, partial improvement in others, and little or no benefit in others. It is a treatment, not a diagnostic test, personality change, memory eraser, or guaranteed cure. A good program discusses what would count as meaningful improvement, when to reassess, and what the next step would be if the first protocol is ineffective.

Safety, Side Effects, and Who Needs Extra Review

Established TMS protocols are generally well tolerated when delivered by trained personnel under appropriate safety guidelines. The most common adverse effects are:

  • Scalp pain, pressure, tingling, or discomfort at the stimulation site
  • Headache
  • Brief contraction of scalp, forehead, jaw, or facial muscles during stimulation
  • Transient lightheadedness or dizziness
  • Temporary discomfort from the sound or sensory intensity of treatment

These effects often improve over the first several sessions or with coil-position and intensity adjustments. Ear protection is used because TMS pulses are loud.1617

Rare but Important Risks

  • Seizure: Therapeutic TMS is not intended to cause a seizure, but seizure is a rare potential adverse event. Risk assessment includes protocol parameters, personal seizure history, brain injury or disease, medications or substances that may lower seizure threshold, sleep deprivation, and alcohol or sedative withdrawal.16
  • Mania or hypomania: Mood activation appears uncommon but can occur, particularly in a person with bipolar disorder or vulnerability to mania. Screening and monitoring matter.
  • Hearing injury: Appropriate hearing protection is required. New persistent hearing change or tinnitus should be reported promptly.
  • Interaction with metal or electronic implants: Ferromagnetic or magnet-sensitive material and electronic devices near the coil can pose risk. Examples that require careful device-specific review include cochlear implants, deep brain stimulators, implanted cranial hardware, aneurysm clips or coils, medication pumps, and retained metal fragments. Not every implant or dental restoration is automatically disqualifying, but patients should never assume compatibility without review.16

New neurological symptoms, loss of consciousness, seizure-like activity, severe or persistent headache, marked mood elevation, psychosis, or rapidly worsening suicidal thoughts require prompt clinical assessment rather than waiting for the next routine TMS visit.

Urgent-care note: Routine outpatient TMS is not a substitute for emergency psychiatric or neurological care. Severe depression with imminent suicide risk, catatonia, psychosis, inability to eat or drink, or another life-threatening presentation may require hospitalization and a faster-acting treatment such as ECT. Call 911 or 988 in the United States when immediate safety is at risk.17

TMS Is Not ECT

TMS and electroconvulsive therapy are both established brain-stimulation treatments, but they should not be described as versions of the same procedure.

FeatureRoutine therapeutic TMSECT
AnesthesiaNo anesthesia or sedation; patient remains awakeShort-acting general anesthesia and a muscle relaxant are used
SeizureA seizure is not intended; seizure is a rare adverse eventA controlled therapeutic seizure is intentionally induced
Cognitive effectsEstablished protocols generally show little risk of clinically significant cognitive impairment; temporary headache, discomfort, or fatigue are more typicalTemporary confusion and memory effects can occur; risk varies with technique and individual factors
Course and recoveryUsually outpatient with little or no recovery time; benefit often develops over repeated sessionsProcedure and recovery monitoring are required; courses are commonly several treatments and can work more rapidly
Clinical roleOften considered for nonpsychotic major depression after inadequate benefit or intolerance from medication, with additional device-specific usesOften favored when depression is very severe, psychotic, catatonic, life-threatening, or requires a rapid response

It is inaccurate to say that TMS has “no seizure risk” or that ECT always causes permanent memory loss. The accurate comparison is that routine TMS does not intentionally produce a seizure and has a very different cognitive and anesthesia profile, while ECT deliberately induces a therapeutic seizure and remains one of the most effective and rapid treatments for severe depressive illness.1617

How Is the Brain Target Chosen?

Targeting matters, but “MRI-guided” can refer to several different things.

Scalp-Based Targeting

Validated external methods use head measurements and landmarks to estimate a cortical target. Beam F3 is a common example for locating a left prefrontal depression target. These methods are practical, do not require MRI, and support evidence-based and FDA-cleared treatment.

Structural-MRI Neuronavigation

A patient’s structural MRI is registered to the head, and an optical tracking system displays the coil relative to the individual’s cortex in real time. This can improve anatomical localization and session-to-session reproducibility. It does not automatically identify the functionally optimal network target, and it does not make the magnetic field pinpoint or cell-specific.2

Functional-Connectivity Targeting

Resting-state functional MRI can be used to identify a prefrontal location based on its connectivity with a depression-related network. The FDA-cleared SAINT system combines structural and functional MRI, individualized targeting, neuronavigation, and a specific accelerated high-dose iTBS schedule to deliver the SNT protocol. The result should be understood as a complete protocol, not as evidence that an MRI alone improves every TMS course.6

In the June 2026 randomized study, 40 adults receiving the same high-dose accelerated treatment were assigned to connectivity-based or Beam F3 targeting. Median depression-score reduction at 1 month was 24 points with connectivity targeting and 18 points with scalp targeting. This is important direct evidence that individualized target selection can affect outcome in that setting. The sample was small, the treatment was unusually intensive, and confirmation in larger and more diverse populations is still needed.9

Balanced conclusion: Structural neuronavigation can provide an anatomical-localization and reproducibility advantage over external-landmark methods when placing a coil over an intended site. Functional-connectivity targeting may further improve outcomes for specific protocols, but the evidence should not be exaggerated into a universal claim that all MRI-guided TMS is clinically superior to all non-MRI targeting.29

Questions to Ask Before Starting TMS

  1. What exact diagnosis and treatment goal are we addressing?
  2. Is this use FDA-cleared for this device, coil, age group, and protocol, or is it off label?
  3. What evidence supports this target and schedule for my condition?
  4. How will motor threshold and the treatment target be determined?
  5. Does “MRI-guided” mean structural neuronavigation, functional-connectivity targeting, or both?
  6. What are the expected common effects, rare risks, and implant restrictions?
  7. How will symptoms and function be measured during the course?
  8. What happens if I improve, partially improve, or do not improve?
  9. What are the alternatives, including medication, psychotherapy, ECT, and clinical trials?
  10. What is the total cost, what is covered, and are maintenance sessions included?

Bottom Line

TMS is a non-surgical, awake treatment that uses magnetic pulses to induce electrical activity in targeted regions of the cerebral cortex and influence connected brain networks. It is not ECT, does not require anesthesia, and does not intentionally induce a seizure. It is generally well tolerated, but it is not risk-free and should be delivered with appropriate screening, hearing protection, dose calibration, and clinical monitoring.

Its most established use is major depressive disorder. Specific devices also have U.S. authorizations for adult OCD, short-term smoking cessation, anxiety symptoms that accompany major depression, adjunctive treatment of adolescent depression ages 15 through 21, single-pulse treatment of migraine, and a device-specific adjunctive adult PTSD protocol. The exact device and label matter.18

The field is becoming faster and more individualized. Three-minute iTBS, five-day accelerated protocols, the May 2026 expansion of accelerated scheduling, and new randomized evidence for connectivity-based targeting are meaningful advances. They do not make every protocol equivalent, eliminate the need for careful diagnosis, or guarantee response.

At Los Altos Neurology, TMS is delivered through a neurologist-led TMS & Neuromodulation Program. Our approach emphasizes accurate diagnosis, individualized safety review, objective outcome tracking, transparent discussion of FDA-cleared versus off-label care, and MRI-guided neuronavigation when it meaningfully supports the treatment plan.

Next in this series: How TMS Works: The Science of Magnetic Brain Stimulation, followed by a history of TMS and detailed reviews of individual clinical applications and their evidence.

References

  1. U.S. Food and Drug Administration. NeuroStar TMS Therapy System: FDA clearance letter and 510(k) summary (K083538). December 16, 2008.
  2. Trapp NT, Purgianto A, Taylor JJ, et al. Consensus review and considerations on TMS to treat depression: a comprehensive update endorsed by the National Network of Depression Centers, the Clinical TMS Society, and the International Federation of Clinical Neurophysiology. Clin Neurophysiol. 2025;170:206-233. doi:10.1016/j.clinph.2024.12.015.
  3. Blumberger DM, Vila-Rodriguez F, Thorpe KE, et al. Effectiveness of theta burst versus high-frequency repetitive transcranial magnetic stimulation in patients with depression (THREE-D): a randomised non-inferiority trial. Lancet. 2018;391(10131):1683-1692. doi:10.1016/S0140-6736(18)30295-2.
  4. U.S. Food and Drug Administration. NeuroStar Advanced Therapy System with NeuroBurst intermittent theta-burst stimulation: 510(k) Summary (K201158). November 20, 2020.
  5. Cole EJ, Phillips AL, Bentzley BS, et al. Stanford Neuromodulation Therapy (SNT): a double-blind randomized controlled trial. Am J Psychiatry. 2022;179(2):132-141. doi:10.1176/appi.ajp.2021.20101429.
  6. U.S. Food and Drug Administration. Magnus Neuromodulation System with SAINT Technology: 510(k) Summary (K220177). September 1, 2022.
  7. U.S. Food and Drug Administration. MagVenture Accelerated TMS Therapy System: 510(k) Summary (K260189). May 22, 2026.
  8. Kratter IH, Austelle CW, Lissemore JI, et al. Stanford neuromodulation therapy for treatment-resistant depression: a randomized controlled trial confirming efficacy, and an EEG study providing insight into mechanism of action and a potentially predictive biomarker of efficacy. World Psychiatry. 2026;25(1):105-116. doi:10.1002/wps.70032.
  9. Taylor JJ, Kare MR, Haj-Darwish D, et al. Connectivity- vs scalp-based targeting of accelerated transcranial magnetic stimulation for depression: a randomized clinical trial. JAMA Psychiatry. Published online June 24, 2026. doi:10.1001/jamapsychiatry.2026.1100.
  10. U.S. Food and Drug Administration. NeuroStar Advanced Therapy System: adjunctive treatment of major depressive disorder in adolescent patients ages 15-21 (K231926). March 22, 2024.
  11. U.S. Food and Drug Administration. De Novo Classification Request for the BrainsWay Deep Transcranial Magnetic Stimulation System for adult obsessive-compulsive disorder (DEN170078). Decision August 17, 2018.
  12. Carmi L, Tendler A, Bystritsky A, et al. Efficacy and safety of deep transcranial magnetic stimulation for obsessive-compulsive disorder: a prospective multicenter randomized double-blind placebo-controlled trial. Am J Psychiatry. 2019;176(11):931-938. doi:10.1176/appi.ajp.2019.18101180.
  13. U.S. Food and Drug Administration. BrainsWay Deep TMS System as an aid in short-term smoking cessation for adults: 510(k) Summary (K200957). August 21, 2020.
  14. U.S. Food and Drug Administration. NeuroStar Advanced Therapy System: treatment of depressive episodes and decreasing comorbid anxiety symptoms in adult major depressive disorder (K222230). August 24, 2022.
  15. U.S. Food and Drug Administration. SAVI Dual Migraine Therapy: acute and prophylactic single-pulse TMS for migraine in adolescents age 12 and older and adults (K230358). May 16, 2023.
  16. Rossi S, Antal A, Bestmann S, et al. Safety and recommendations for TMS use in healthy subjects and patient populations, with updates on training, ethical and regulatory issues: expert guidelines. Clin Neurophysiol. 2021;132(1):269-306. doi:10.1016/j.clinph.2020.10.003.
  17. National Institute of Mental Health. Brain Stimulation Therapies. Accessed July 10, 2026.
  18. U.S. Food and Drug Administration. MeRT System for adjunctive treatment of adult PTSD: 510(k) Summary (K260402). June 3, 2026.

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