The most common side effects of TMS are headache and pain or discomfort on the scalp where the coil sits. They are usually mild to moderate, happen during the treatment course rather than lingering for months, and tend to ease after the first week. Twitching of face or jaw muscles during pulses and brief lightheadedness also occur.
The most serious risk is a seizure, which is rare: in one large survey, fewer than 1 seizure per 60,000 sessions when TMS was given within safety guidelines to people without known risk factors. "No side effects" is not an honest claim for TMS; "side effects are usually mild and temporary" is.
Side effects at a glance
| Side effect | How often (best available data) | What usually happens |
|---|---|---|
| Headache | 26.7% with active deep TMS vs 18.9% with sham in its main trial | Mild, during the course; often eases as treatment continues |
| Pain or discomfort at the treatment site | The most common complaint in the NeuroStar trials; 5.0% vs 0% for application-site pain in the deep TMS trial | Mostly in the first week; for most people it does not continue after that |
| Eye pain, toothache, muscle twitch, facial pain, skin pain | Each at least 5% and at least twice the sham rate in NeuroStar trials | During the session; stops when pulses stop |
| Stopping treatment because of side effects | 4.5% in the pivotal NeuroStar trial | Most people complete the course |
| Hearing change | No change found when hearing protection was used | Prevented by well-fitted earplugs |
| Mania or hypomania | Not significantly different from sham in pooled trials | Most reported cases were in bipolar disorder |
| Seizure | Under 1 per 60,000 sessions within guidelines, without risk factors | Rare; most likely in the first few sessions |
One caution about the numbers: trial figures depend on the device, the protocol and how side effects were asked about, so treat them as a guide rather than a prediction for you.
Headache and scalp pain: the side effects most people notice
Scalp discomfort is location- and intensity-dependent, which means it depends on where the coil sits and how strong the pulses are. It tends to be worst in the early sessions. Headache is common enough that both arms of the large THREE-D trial, which compared two active forms of TMS, reported it in roughly two-thirds of patients (64% and 65%). That trial had no sham group, so some of those headaches would likely have happened anyway.
How teams usually manage it:
- Building up gradually. For people who are very sensitive to the sensation, many clinicians use a gradually increasing dose over the first week.
- Time. Patients generally develop tolerance to the discomfort over the first two weeks.
- A short rest. If you have a headache after a session, the team may have you rest a few minutes before leaving.
- Pain relief, after checking. Ask your psychiatrist which over-the-counter pain reliever, if any, suits your other medications.
What these sensations are actually like is described in what TMS feels like.
Seizure risk: the honest number
Seizure is the most serious acute side effect of TMS, and it is rare. International experts concluded in 2021 that, given how many people have had TMS and how few seizures have been reported, the risk "is certainly very low". A survey covering 2012 to 2016 estimated 24 seizures across about 318,560 sessions; when TMS was given within guidelines to people without risk factors, the rate was under 1 per 60,000 sessions. NeuroStar's safety information puts the per-patient risk at under 0.1%, which is fewer than 1 in 1,000 patients.
Risk is not identical for everyone. It rises with risk factors such as epilepsy or brain lesions, and seizures were most likely within the first few sessions. A 2018 survey of Clinical TMS Society members found a higher seizure rate per patient with the deep TMS H-coil (5.56 per 1,000 patients) than with the three most-used figure-8 devices combined (0.14 per 1,000), although the authors called the absolute risk low; only 134 of about 500 members responded. Things that can lower the seizure threshold include alcohol withdrawal, recreational stimulants such as cocaine, sleep deprivation and certain medical problems such as very low sodium. In the main deep TMS trial, the one seizure followed undisclosed heavy drinking the night before, and the patient recovered fully. The physician's guide has the full data in TMS safety and seizure risk.
Fainting is different from a seizure. Some people feel faint, and a faint can include a few jerks that look like a seizure; it is managed by lowering the head, fluids, cooling and reassurance.
Hearing
Each TMS pulse makes a loud click, with peaks measured close to the 140 dB safety limit for impulsive noise. That is why FDA guidance requires earplugs or similar protection rated for 30 dB of noise reduction for every session. With protection, studies found no change in hearing, and NeuroStar's development program found no change in hearing thresholds. The one reported case of a small permanent hearing change followed an earplug slipping out. If you notice hearing loss, ringing or ear fullness after a session, tell the team; you should have a hearing check.
Mood switching into mania
Any effective antidepressant treatment raises the question of tipping someone into mania or hypomania. For TMS, pooled trials have not found a significant difference from sham: a 2021 analysis of 25 blinded trials found no significant difference in switch rates. An earlier analysis found rates under 1% with both active and sham treatment, and most reported cases involved bipolar disorder. FDA guidance still lists bipolar disorder as a group where evidence on efficacy and safety is lacking, so people with bipolar disorder need specialist judgment before TMS. The physician's guide covers TMS for bipolar depression.
Device labeling also carries a warning to watch for worsening depression or suicidal thinking during treatment, as with any depression treatment. If you are thinking about suicide or are in crisis, call or text 988 (the 988 Suicide & Crisis Lifeline) or go to the nearest emergency room.
Memory and thinking
A systematic review cited by international safety guidelines found no reliable evidence of cognitive side effects across 31 randomized trials of this kind of TMS. NeuroStar's development program also found no change in cognitive function. This is one of the clearest practical differences from ECT, which can cause memory loss that was still detectable six months after treatment in one study of New York City-area facilities. More detail is in does TMS affect memory or thinking.
What TMS side effects look like next to medication side effects
Antidepressants circulate through the whole body. Common side effects of SSRIs and other antidepressants include upset stomach, headache and sexual dysfunction, though they are generally mild and often ease with time. The side effects reported for TMS in the trials and safety summaries above are different in kind: mostly at the head, during the course of treatment. Weight change and sexual side effects do not appear among the TMS side effects listed in those trial reports and device safety summaries.
That does not make TMS risk-free, and it is not a reason to stop a medication that is working. Long-term side effects of TMS have not been fully determined, and more research is needed. If side effects drove you off antidepressants, see where TMS fits after medication side effects, and for combining the two, medications during TMS.
Side effects in particular groups
Pregnancy. Treating depression during pregnancy is not a specifically cleared use of TMS. FDA guidance lists pregnant or nursing patients as a group where evidence is lacking, which is a precaution rather than a ban. International guidelines call TMS "minimal risk" for mother and child, a cautious conclusion based mostly on figure-8 coil data; the main theoretical risk to the fetus is a maternal seizure. In published reports covering 50 pregnant patients, side effects were mild and mostly scalp pain and headache. The evidence is small, though: in the one sham-controlled trial, with 22 women, three late preterm births occurred, all in the active TMS group, and the authors said a link could not be excluded without larger trials. Safety data for the deep TMS H-coil in pregnancy are not yet available. See TMS during pregnancy and after birth.
Teens and young adults. In the only large sham-controlled trial in adolescents and young adults (ages 12 to 21), there were no new safety signals. The guide to TMS for teens and young adults covers the evidence and the cleared age range.
What about reports in FDA's adverse event database?
You may see headlines about TMS reports in FDA's MAUDE database. A 2026 analysis of that database found 200 unique reports for depression TMS devices through April 2025, with anxiety, cognitive complaints, seizures, headache and tinnitus among the most commonly reported symptoms. These reports are not verified and cannot tell you how often a problem happens, because nobody knows how many treatments were given in total. They are a signal to keep watching, not a rate.
Lowering your risk
- Tell the team about every medication, supplement and recreational drug, and any change during the course.
- Report any history of seizures, head injury, stroke or other neurologic illness; FDA guidance calls for close monitoring in these situations.
- Disclose metal or implants in or near your head; some are contraindications. See fillings, implants and tattoos.
- Keep sleep regular and avoid heavy drinking during the course. See caffeine, alcohol and sleep during TMS.
- Keep your earplugs in for every session.
When to call the TMS team or clinician
Call the same day if you have a headache that is severe or will not ease, hearing changes or ringing, fainting, any seizure-like episode, new confusion, or a mood change that worries you, such as racing thoughts, little need for sleep or depression getting worse. 911 is the right call for a seizure that lasts more than a few minutes or any other emergency.
For more on deciding whether TMS is right for you, browse the TMS patient guide or read about TMS therapy.
Sources
- Effectiveness of theta burst versus high-frequency repetitive transcranial magnetic stimulation in patients with depression (THREE-D): a randomised non-inferiority trial. The Lancet, 2018. pubmed.ncbi.nlm.nih.gov
- Left prefrontal transcranial magnetic stimulation for treatment-resistant depression in adolescents: a double-blind, randomized, sham-controlled trial. Neuropsychopharmacology, 2021. pubmed.ncbi.nlm.nih.gov
- Safety and recommendations for TMS use in healthy subjects and patient populations, with updates on training, ethical and regulatory issues: Expert Guidelines. Clinical Neurophysiology, 2021. europepmc.org
- Seizures from transcranial magnetic stimulation 2012-2016: Results of a survey of active laboratories and clinics. Clinical Neurophysiology, 2019. europepmc.org
- Seizure risk with repetitive TMS: Survey results from over a half-million treatment sessions. Brain Stimulation, 2021. europepmc.org
- Safety Information. Neuronetics (NeuroStar), 2026. neurostar.com
- 166 Post Market Rate of Seizures During TMS Treatment with NeuroStar System Appears to Be Lower than Previously Estimated. CNS Spectrums, 2020. cambridge.org
- Efficacy and safety of deep transcranial magnetic stimulation for major depression: a prospective multicenter randomized controlled trial. World Psychiatry, 2015. pmc.ncbi.nlm.nih.gov
- Class II Special Controls Guidance Document: Repetitive Transcranial Magnetic Stimulation (rTMS) Systems. U.S. Food and Drug Administration, 2011. fda.gov
- Efficacy and safety of transcranial magnetic stimulation in the acute treatment of major depression: a multisite randomized controlled trial. Biological Psychiatry, 2007. pubmed.ncbi.nlm.nih.gov
- Transcranial magnetic stimulation in the treatment of major depressive disorder: a comprehensive summary of safety experience from acute exposure, extended exposure, and during reintroduction treatment. Journal of Clinical Psychiatry, 2008. europepmc.org
- Side Effects. Neuronetics (NeuroStar), 2026. neurostar.com
- Treatment-emergent mania in unipolar and bipolar depression: focus on repetitive transcranial magnetic stimulation. International Journal of Neuropsychopharmacology, 2008. europepmc.org
- Hypomanic/manic switch after transcranial magnetic stimulation in mood disorders: A systematic review and meta-analysis. World Journal of Psychiatry, 2021. europepmc.org
- Postmarketing Safety of Transcranial Magnetic Stimulation: A 10-Year MAUDE Database Analysis of Adverse Events and Technological Advancements. Journal of Clinical Psychiatry, 2026. pubmed.ncbi.nlm.nih.gov
- Brain Stimulation Therapies. National Institute of Mental Health, 2024. nimh.nih.gov
- Transcranial Magnetic Stimulation (TMS). Cleveland Clinic, 2026. my.clevelandclinic.org
- The Clinical TMS Society Consensus Review and Treatment Recommendations for TMS Therapy for Major Depressive Disorder. Brain Stimulation, 2016. pmc.ncbi.nlm.nih.gov
- Mental Health Medications. National Institute of Mental Health, 2023. nimh.nih.gov
FAQs
How long do TMS side effects last?
Most are short-lived: scalp discomfort and twitching happen during sessions, and headaches are usually mild and temporary. For most people treatment-site discomfort stops being a problem after the first week.
Can TMS cause brain damage?
Safety guidelines identify a rare seizure as the most serious acute risk, and reviews found no reliable evidence of cognitive side effects from standard TMS for depression. Long-term effects have not been fully determined, which is worth knowing.
Does TMS cause weight gain?
Weight gain is not among the side effects listed in the main TMS trial reports and device safety summaries. If you are already on a medication that affects weight, TMS will not change that.
Is deep TMS riskier than standard TMS?
A clinic survey found a higher seizure rate per patient with the deep TMS H-coil than with common figure-8 devices, though the absolute risk was low for both. Your team should explain the device they use and why.
Can I have TMS if I have had a seizure before?
Possibly, but it needs careful evaluation. A seizure history raises risk, and FDA guidance calls for close monitoring, so discuss it with a psychiatrist before starting.
