Transcranial magnetic stimulation (TMS) is considered safe. It was first cleared by the FDA in 2008 for treating major depression, and serious complications are exceptionally rare. The most common side effects, headache and mild scalp discomfort, affect fewer than 1 in 10 people and typically fade within the first few sessions. Unlike medications, TMS has no systemic effects on your organs, blood pressure, or heart rate, and unlike electroconvulsive therapy, it requires no sedation or recovery time.
What Side Effects to Expect
The side effects most people experience during TMS are mild and localized to the treatment area. In clinical studies, about 7 to 10 percent of patients report headache, and roughly 3 to 9 percent notice discomfort at the spot on the scalp where the magnetic coil sits. A small number of people (around 2 percent) experience facial twitching during pulses, and a similar percentage feel drowsy afterward. These effects tend to decrease over the course of treatment as your scalp adjusts to the sensation.
Older adults appear to tolerate TMS at least as well as younger patients. In a review of 331 older adults receiving treatment, headache rates were about 7 percent and scalp discomfort dropped to under 3 percent. No unique age-related safety concerns emerged.
There are no effects on the rest of your body. Research specifically examining cardiac safety found that TMS does not alter blood pressure or heart rate. You won’t experience the weight gain, sexual dysfunction, nausea, or fatigue that commonly accompany antidepressant medications.
The Seizure Risk Is Extremely Low
Seizure is the most serious potential risk of TMS, and it’s the one people worry about most. The actual numbers are reassuring. A large survey covering over 318,000 TMS sessions found 24 seizures total, putting the risk at roughly 1 in 60,000 sessions for people without additional risk factors. That translates to about 0.008 percent.
The risk varies slightly by the type of coil used. Standard figure-8 coils carry the lowest seizure rate (about 0.08 per 1,000 sessions), while H-coils used in deep TMS have a somewhat higher but still very low rate (0.43 per 1,000). In every case, TMS-related seizures are isolated events, not a sign of developing epilepsy. They resolve on their own and do not typically recur.
No Evidence of Cognitive Harm
One reasonable concern is whether repeated magnetic pulses could damage brain function over time. The evidence points in the opposite direction. Studies in patients with mild cognitive impairment and Alzheimer’s disease found that TMS actually improved cognitive performance compared to sham treatment, both immediately and at longer follow-ups. In healthy individuals and depression patients, neuropsychological testing consistently shows no decline in memory, attention, or processing speed after full courses of treatment.
Who Should Not Get TMS
The main absolute contraindication is metal inside or near your head. Intracranial metal implants, skull plates, and aneurysm clips can interact dangerously with the magnetic field. Cochlear implants are also a concern and generally rule out treatment unless a detailed safety analysis is performed.
Implanted devices located in the neck or torso, such as cardiac pacemakers, vagus nerve stimulators, or spinal cord stimulators, are a different story. TMS can be safely delivered as long as the coil stays more than 10 centimeters from the electronic components of the device. Your provider will ask about all implants during the screening process. A personal or family history of seizures is another important factor that needs to be discussed, though it doesn’t automatically disqualify you.
Hearing Protection Matters
Each TMS pulse produces a loud clicking sound. Depending on the device and intensity, peak sound levels at the coil surface range from about 80 to 94 decibels, comparable to a lawnmower or heavy traffic. At higher intensities or with certain equipment, the sound can theoretically exceed 120 decibels. For this reason, both patients and operators wear earplugs during every session. With proper ear protection in place, no hearing-related complications have been reported in routine clinical use.
Standard TMS vs. Deep TMS
Two main forms of TMS are used clinically. Standard repetitive TMS (rTMS) uses a figure-8 coil that targets brain areas close to the skull surface. Deep TMS (dTMS) uses a helmet-shaped H-coil that reaches structures further beneath the surface. In head-to-head comparisons, the two techniques show similar safety profiles. Both are FDA-cleared, and neither produces significantly more side effects than the other. The choice between them depends on the condition being treated and what your provider has available, not on safety differences.
Safety During Pregnancy
For pregnant women dealing with depression, TMS offers an important advantage: it doesn’t involve medication that crosses the placenta. Studies of TMS during pregnancy have found significant reductions in depression scores with minimal adverse effects on either mother or baby. Most trials reported no adverse neonatal outcomes. One study noted three preterm births among 22 participants, but all other neonatal outcomes were normal. While the evidence base is still growing, TMS is increasingly viewed as a viable option when avoiding medication during pregnancy is a priority.
What a Session Feels Like
A typical TMS session lasts between 20 and 40 minutes. You sit in a chair, fully awake, with no anesthesia or sedation. The magnetic coil is positioned against your head, and you feel a tapping or knocking sensation on your scalp with each pulse. Some people find the first few sessions uncomfortable, but most adjust quickly.
There is no recovery period afterward. You can drive yourself home, go back to work, or continue your day without restrictions. This is a meaningful practical difference from treatments like electroconvulsive therapy, which requires anesthesia and a recovery window. Most treatment courses involve sessions five days a week for four to six weeks, though newer accelerated protocols can compress that timeline significantly.
FDA-Cleared Uses
The FDA has cleared TMS for three conditions: major depression (2008), migraine pain (2013), and obsessive-compulsive disorder (2018). It is also used off-label for conditions like anxiety, PTSD, and smoking cessation, with varying levels of supporting evidence. The FDA clearance process for TMS specifically evaluates safety data, so these approvals reflect over 15 years of accumulated clinical evidence showing the treatment’s risk profile is low.