Everything you need to know about TMS Side Effects: What Is Normal and What Requires Attention — how it works, what it costs, and how to find a provider who actually knows what they're doing.
Every effective treatment has side effects. TMS is no exception. Understanding the difference between expected, mild discomfort and signs that something is wrong is important for getting through a treatment course and for staying safe.
The good news is that TMS side effects are generally mild and transient. Most patients who experience any side effects describe them as manageable and diminishing over the first week or two of treatment. Severe side effects are rare.
Common Side Effects (Mild and Expected)
Headache
This is the most common TMS side effect, affecting roughly 40-50% of patients. The headache is typically:
- Mild to moderate in intensity
- Located at the site of stimulation (forehead/temple)
- Described as a throbbing or pressure sensation
- Worst after the first few sessions
- Usually diminishing significantly by the second week
What helps: Acetaminophen or ibuprofen (check with your doctor if you have any medication contraindications). Some patients find that adjusting the coil position slightly (your technician can do this) reduces headache. Staying hydrated also helps.
A headache that persists for more than 24-48 hours after a session, or a headache that worsens significantly over the course of treatment, warrants discussion with your clinician.
Scalp Discomfort at the Stimulation Site
Tingling, warmth, or mild pain at the coil site during stimulation is normal. Some patients describe it as a tapping or knocking sensation. This is caused by the superficial stimulation of scalp nerves and muscles, not by the brain stimulation itself.
What helps: Inform your technician if the discomfort is significant. Small adjustments to coil positioning or angle can often reduce this. It typically diminishes as you acclimate to the sensation.
Muscle Twitching
Facial or scalp muscle contractions during stimulation are expected and normal. The magnetic field activates motor neurons in the targeted cortex, which causes the muscles controlled by those neurons to contract.
What helps: This is expected and requires no intervention. If the twitching is painful or distressing, let your technician know — they can adjust the intensity slightly.
Fatigue After Sessions
Some patients feel tired after TMS sessions, particularly in the first few weeks. This is likely related to the cumulative effect of daily stimulation on neural circuits and the brain’s plastic response process.
What helps: Schedule sessions at a time of day that accommodates post-session fatigue. If you are severely fatigued, discuss it with your clinician — lowering the intensity slightly may help.
Lightheadedness
A brief, mild sensation of lightheadedness during or immediately after sessions is reported by some patients. This is typically transient and resolves within minutes.
What helps: If lightheadedness is significant, sit for a few minutes after the session before standing. Let your technician know so they can verify the intensity setting.
Less Common Side Effects
Changes in Hearing
The loud clicking sound produced by the TMS coil can reach 100-120 dB at the ear. With proper ear protection (foam earplugs or equivalent), this is safe. Some patients report mild, transient muffled hearing or tinnitus immediately after sessions.
What helps: Consistent use of earplugs during every session. If hearing changes persist beyond a few hours after a session, inform your clinician and consider audiology evaluation.
Seizure
Seizure is the most serious known risk of TMS. The estimated risk in clinical settings is approximately 1 in 30,000 to 1 in 60,000 sessions. This is extremely low but not zero. Risk factors include:
- Lowering the seizure threshold: certain medications (e.g., tricyclic antidepressants, some antipsychotics), alcohol withdrawal, sleep deprivation
- Higher stimulation intensity relative to motor threshold
- Rapid frequency of stimulation
- Pre-existing seizure disorder (a relative contraindication)
What you should know: A TMS seizure is a medical emergency. Reputable clinics have protocols in place for this event. The seizure is typically self-limited, but emergency protocols should be available.
Your clinic should screen for seizure risk factors before treatment. If you have a history of seizure, disclose it fully. Some patients with controlled seizure disorders on stable medication can receive TMS safely with modified protocols; others cannot.
Manic Switch (in Bipolar Patients)
Patients with bipolar disorder are at risk of switching into mania or hypomania during TMS treatment. This is a known risk, and patients with bipolar history should be monitored for manic symptoms during treatment.
What helps: Careful screening for bipolar history before treatment, monitoring with standardized mania rating scales during treatment, and having a protocol for managing switches if they occur.
Worsening Depression or Anxiety
Some patients experience a temporary worsening of depressive or anxious symptoms in the first week or two of TMS. This is not universal, and when it occurs, it typically resolves spontaneously.
What helps: If significant worsening occurs, inform your clinician. Sometimes a brief medication adjustment, session frequency change, or other modification helps.
Symptoms That Require Immediate Medical Attention
Call your clinician or go to urgent care if you experience:
- A seizure (any type — even brief)
- Severe or worsening headache that does not respond to pain medication
- Sudden changes in vision, speech, or motor function
- Hearing changes that persist for more than a few hours after a session
- Symptoms of mania in bipolar patients (elevated mood, decreased need for sleep, racing thoughts, impulsive behavior)
- Significant worsening of suicidal thoughts
Call 911 if you are in crisis. If TMS is triggering suicidal thinking, you need immediate support. Do not wait for your next appointment.
Medication Interactions That Increase Side Effect Risk
Some medications lower the seizure threshold or interact with TMS mechanisms. Common ones to disclose:
- Tricyclic antidepressants (imipramine, amitriptyline, nortriptyline)
- Some antipsychotics (clozapine, chlorpromazine)
- Stimulants (amphetamine, methylphenidate)
- Alcohol (particularly during withdrawal)
Your TMS clinician should review all medications before treatment. Full disclosure is essential for safe treatment.
The Bottom Line on Side Effects
TMS is one of the better-tolerated psychiatric treatments in terms of side effect burden. Most patients experience mild, transient headache or scalp discomfort. Serious side effects are rare when proper screening and protocols are followed.
The key is communication. Your treatment team should know about every side effect you experience, even mild ones. Many are manageable with small adjustments to parameters or positioning. The goal is a complete treatment course with minimal discomfort — and communication is how you get there.
If a side effect is intolerable, discuss it with your clinician rather than simply stopping treatment. There are almost always adjustments that can help.