Are there any risks with TMS? Yes, Transcranial Magnetic Stimulation (TMS) has risks. But serious complications are very rare when treatment follows established safety guidelines. The biggest concern, seizures, occurs in fewer than 0.02 cases per 1,000 treatment sessions among people without known risk factors.
Most people experience milder side effects such as scalp discomfort, headache, lightheadedness, or facial muscle twitching, and these symptoms usually improve within days to a week. Keep reading to see what the research says about TMS risks, long-term safety, and who should avoid this treatment.
Key Takeaways
- The seizure risk is statistically minimal with proper screening.
- Common side effects are typically mild and improve quickly.
- Specific medical histories and devices can make TMS unsafe.
The Most Common Experience: Mild and Manageable Side Effects
Most patients walk into a TMS clinic with one primary fear lodged in the back of their mind. They’ve read about magnetic fields and brains, and they’re braced for something dramatic. The reality is usually far less dramatic, and understanding the true safety profile of TMS helps separate evidence from misconception. The majority of side effects are local and temporary, a direct result of the physical mechanics of the treatment.
You feel a tapping sensation on your scalp, a persistent knocking right where the coil is placed. It’s not painful for most, more of a pronounced tapping. This can lead to a mild headache, a dull tension that wraps around the forehead. Think of it like the headache you might get after squinting under bright lights for too long. It’s your scalp muscles responding to the repetitive magnetic pulses.
For about a quarter of patients, the pulses cause temporary eyebrow or jaw muscle twitching during stimulation, which stops immediately when the stimulation ends.
These sensations aren’t a sign something is wrong. They’re simply the expected physical feedback. A good technician will check in frequently, asking about comfort and making micro-adjustments to the coil’s angle or the chair’s position. They might offer a different type of padding. Often, that’s all it takes to reduce the sensation significantly. The body also adapts. Many patients report that what felt strange in week one feels entirely normal by week three.
The initial novelty and anxiety fade, and with them, much of the perceived discomfort.
- Scalp tenderness or aching at the treatment site
- Mild tension headaches during or after sessions
- Transient lightheadedness immediately following treatment
- Temporary, localized facial muscle twitching
The key point is that these effects are almost always self-limiting. They don’t require medical intervention beyond perhaps an over-the-counter pain reliever. They certainly don’t prevent you from driving home or returning to your daily routine. This benign profile is a cornerstone of why TMS is considered a well-tolerated outpatient procedure.
It lacks the systemic side effects,weight gain, sexual dysfunction, and gastrointestinal issues, that so often plague psychiatric pharmacology.
Understanding the Serious but Rare Risks
A thorough discussion of TMS must address the serious, though uncommon, risks. The most significant of these is the induction of a seizure, which is the primary event safety protocols are designed to prevent. For patients without specific risk factors treated within established guidelines, the incidence is extremely low.
A review of more than 300,000 TMS sessions found an overall seizure risk of about 0.08 per 1,000 sessions, and fewer than 0.02 per 1,000 sessions when modern safety guidelines were followed.
Data from the Clinical TMS Society demonstrates:
“the absolute risk of a seizure with rTMS is low,” though the risk can vary depending on the type of coil used . – Clinical TMS Society
This means seizure risk remains low across both clinical practice and research settings when patients are appropriately screened.
Notably, when seizures have occurred, they most often present early in the treatment course, frequently during the initial mapping or first few sessions, which is why these visits involve careful calibration and monitoring.
The risk profile is not uniform. Key factors that can modulate seizure risk include:
- A history of epilepsy or other seizure disorder.
- Extreme sleep deprivation.
- Recent withdrawal from alcohol or benzodiazepines.
- The concurrent use of specific medications known to lower seizure threshold, such as high-dose bupropion or clozapine.
A comprehensive pre-treatment screening is conducted to identify and manage these factors.
Another serious but preventable risk is acoustic injury. The magnetic coil generates a loud click with each pulse, often exceeding 100 decibels. The coil can produce clicks above 100 decibels, which is comparable to a motorcycle or loud power tool.
Without proper protection, repeated exposure could lead to temporary hearing changes or tinnitus.
Research from Brain Stimulation shows:
“can potentially cause hearing loss” . – Brain Stimulation
The safety standard is mandatory: patients must wear earplugs with a Noise Reduction Rating (NRR) of at least 30 decibels for every session.
There is also a recognized, though rare, risk of inducing a manic or hypomanic episode in individuals with an undiagnosed or unstable bipolar disorder. This underscores the necessity of a comprehensive psychiatric evaluation, including screening for bipolarity, prior to initiating TMS therapy.
Serious TMS Risks at a Glance
| Risk | How Common Is It? | What Reduces the Risk? |
| Seizure | Fewer than 0.02 per 1,000 treatment sessions when established safety guidelines are followed | Careful patient screening, medication review, proper stimulation settings, and close monitoring during early sessions |
| Hearing changes or tinnitus | Rare when hearing protection is used | Wear earplugs with a Noise Reduction Rating (NRR) of at least 30 dB during every treatment session |
| Mania or hypomania | Rare, primarily in patients with bipolar disorder | Comprehensive psychiatric evaluation and bipolar disorder screening before treatment |
| Temporary worsening of mood (“TMS dip”) | Reported by some patients, usually during weeks 3–4 | Ongoing communication with the treatment team and protocol adjustments when clinically appropriate |
Notably, when seizures have occurred, they most often present early in the treatment course, frequently during the initial mapping or first few sessions, which is why these visits involve careful calibration and monitoring.
How Clinics Reduce TMS Risks
The low rate of serious complications isn’t based on luck. It reflects the truth about TMS therapy : careful screening, standardized treatment protocols, and close monitoring are what make serious complications so uncommon.
Before treatment begins, clinicians review your medical history, current medications, and any conditions that could increase the risk of complications. They also screen for implanted medical devices, seizure disorders, and other factors that may make TMS unsuitable or require additional precautions.
During the first appointment, your provider performs motor threshold mapping to determine the lowest amount of magnetic stimulation needed to produce a response. That measurement is then used to personalize treatment settings instead of relying on a one-size-fits-all approach.
Every session includes consistent coil placement, hearing protection, and ongoing monitoring for comfort or unexpected reactions. These steps may seem routine, but they’re a big reason why serious TMS complications remain uncommon when treatment follows established clinical guidelines.
- Medical history review
- Medication screening
- Motor threshold mapping
- Personalized stimulation settings
- Hearing protection
- Continuous clinical monitoring
Patient-Reported Experiences and the “TMS Dip”
Online patient forums often discuss experiences that aren’t always detailed in clinical literature. One of the most commonly reported phenomena is the “TMS dip.” This describes a temporary period, often around weeks three or four of a standard six-week course, where mood appears to deteriorate. Patients report a resurgence of depressive symptoms, sometimes with increased irritability or anxiety.
When reported, the TMS dip is usually temporary and often occurs during weeks three to four of treatment.
Clinically, this is not necessarily an indication of treatment failure. Some psychiatrists hypothesize it may represent a transitional phase in neuroplasticity, a period of reorganization as brain circuits adapt to the stimulation. Patients undergoing TMS therapy treatment should continue attending scheduled sessions unless their provider recommends otherwise.
However, any significant worsening of mood, particularly if it includes an increase in suicidal thoughts, must be reported immediately to the treatment team while continuing TMS therapy under your provider’s supervision.
If you suspect this phase, inform your doctor directly. It may prompt a temporary protocol adjustment or increased support, but it does not inherently signify the treatment isn’t working.
Other patient-reported concerns exist in a less defined evidential space. These can include:
- Prolonged emotional blunting or a sense of depersonalization.
- Persistent “brain fog” or cognitive cloudiness.
- Altered sensitivity to stimulants like caffeine.
It is critical to acknowledge these reports as valid patient experiences. However, it is equally important to note that large-scale, controlled studies have not consistently identified these as direct, long-term effects of TMS. While not ruled out, a conclusive causal link has not been established. These experiences may relate to the underlying illness, concurrent treatments, or individual biological variation.
They highlight the necessity of sustained, open communication with your provider throughout the treatment process.
Absolute Contraindications: When TMS Is Not an Option
Safety in TMS isn’t just about managing risk. It also involves understanding the conditions treated by TMS therapy and recognizing when certain medical conditions or implanted devices make treatment inappropriate.
There are clear, non-negotiable contraindications, primarily related to the powerful magnetic field generated by the coil. The safety rule is straightforward: any conductive, ferromagnetic, or magnetic-sensitive metal implanted in or near the head poses a potential hazard.
The concern is twofold: movement and heating. A loose ferromagnetic object could theoretically shift under the magnetic force, though this is more a concern with older aneurysm clips or shrapnel. More consistently, the rapidly changing magnetic field can induce electrical currents in conductive materials, leading to localized heating. This is why patients with certain implanted devices are excluded.
The safety perimeter is defined as within 30 centimeters (about 12 inches) of the treatment coil. Devices that fall within this exclusion zone include:
- Cochlear implants
- Deep brain stimulators (DBS)
- Vagus nerve stimulators (VNS) with leads near the head
- Aneurysm clips or coils in the brain
- Implanted bullet fragments or shrapnel in the skull region
It’s important to distinguish these from common metallic objects. Dental work, such as fillings, crowns, and titanium implants, is generally not a concern. However, while standard dental fillings are safe, permanent metal retainers or non-titanium braces require an extra look, so always let your clinician inspect them during screening. These materials are not strongly ferromagnetic and are firmly anchored.
Similarly, orthopedic joints like hip or knee replacements are far from the treatment site and pose no risk. The screening process involves a detailed medical history review, and when in doubt, clinics will request surgical records or utilize ferromagnetic detectors.
The Onward Psychiatry Protocol: A Case Study in Risk Mitigation
At Onward Psychiatry, TMS safety is established through structured protocols and continuous oversight, beginning well before treatment initiation. The initial consultation involves a comprehensive review of medical history, current medications, and prior treatment responses to determine whether TMS therapy for depression is an appropriate treatment option.
This is a diagnostic interview, not a formality, intended to identify any contraindications or necessary precautions.
The clinic employs the NeuroStar Advanced Therapy system, an FDA-cleared device with integrated safety features. The treatment protocol is a controlled application. Each course begins with a precise motor threshold determination to identify the minimum magnetic energy required to elicit a slight movement in the patient’s right thumb. Treatment is then delivered at a personalized percentage of this threshold to ensure an effective yet conservative dose.
Every treatment session is conducted by a trained technician under direct psychiatrist supervision. Patient comfort and any immediate reactions are monitored in real time. The mandatory use of high-grade ear protection is strictly enforced. The clinic’s integrated tools enable accurate coil placement and session-by-session tracking to maintain consistency.
This systematic method, from screening to dosing to session management, demonstrates how clinical practice implements established safety guidelines. Key components of this approach include:
- A thorough diagnostic interview to identify risk factors.
- Personalized dosing based on motor threshold measurement.
- Direct clinical supervision during every session.
- Strict adherence to hearing protection standards.
Making the Right Choice for Your Mental Health
If you’re thinking about TMS, it’s normal to have questions about safety. The good news is that serious risks are rare for people who qualify after proper screening, and most side effects are short-lived. That’s what matters.
If you’re ready to see whether TMS is the right fit, Onward Psychiatry offers personalized evaluations, evidence-based care, and advanced treatment options to help you move forward with confidence. Schedule your consultation today and learn how their team can guide your next step. Visit Onward Psychiatry to get started.
FAQs
Can TMS cause mood or emotional changes during treatment?
Some people notice temporary mood swings, emotional changes, or a short-term increase in anxiety during treatment. In rare cases, there is a risk of mania or hypomania, especially in people with bipolar disorder. Careful screening before treatment and regular monitoring during sessions help providers respond quickly if emotional changes occur.
What should I expect after a TMS session?
Most post-treatment symptoms are mild and short-lived. Some people experience a mild headache, scalp discomfort, dizziness, lightheadedness, fatigue after a session, nausea, or mild sleep disturbances. These effects usually improve within hours. If symptoms become severe or last longer than expected, contact your healthcare provider for advice.
How do clinics reduce the risk of seizures during TMS?
Although seizures during TMS are rare, clinics follow strict monitoring precautions to improve safety. Providers review seizure history, identify individual risk factors, and explain emergency procedures before treatment starts. Following safety protocols, appropriate stimulation settings, and ongoing monitoring helps keep the overall risks very low.
How is TMS treatment kept safe from start to finish?
Treatment safety depends on trained staff, proper equipment, and established procedures. Operator training, clinical oversight, and strict safety protocols help reduce adverse events and rare complications. Clinics also follow regulatory approval standards, review relevant FDA warnings, monitor for any device malfunction, and document care throughout the treatment process.
References
- https://ichgcp.net/de/clinical-trials-registry/publications/283155-seizure-risk-with-repetitive-tms-survey-results-from-over-a-half-million-treatment-sessions
- https://pubmed.ncbi.nlm.nih.gov/24582370/
Related Articles
- https://www.onwardpsychiatry.com/tms-therapy/
- https://www.onwardpsychiatry.com/tms-therapy-for-depression/
- https://www.onwardpsychiatry.com/post/what-is-the-success-rate-of-tms/
- https://www.onwardpsychiatry.com/blog/what-conditions-can-tms-treat/
