Side Effects of Transcranial Magnetic Stimulation (TMS) for Treatment-Resistant Depression
TMS is remarkably safe and well-tolerated with minimal side effects, particularly when compared to antidepressant medications—adverse effects are rare, mild, and transient, with no systemic side effects or drug-drug interactions. 1, 2, 3
Common Side Effects
Mild and Transient Effects
- Headache and scalp discomfort are the most frequently reported side effects during TMS treatment 4
- Skin irritation at the stimulation site can occur but is preventable when standard protocols are followed 1
- These effects are typically self-limited and do not require treatment discontinuation 2
Cognitive Effects During Treatment
- Temporary memory difficulties may occur during active treatment sessions, particularly with high-frequency stimulation (≥10 Hz) 5
- High-frequency TMS (10-20 Hz) can temporarily interrupt accuracy in tasks involving attention, executive functions, memory, and perception during the stimulation period 5
- These cognitive effects are transient and resolve after the treatment session ends 5
- Importantly, some studies demonstrate cognitive improvements rather than impairments with TMS treatment 6
Serious Adverse Events
Seizure Risk
- Seizure is the most serious potential adverse event, but risk is minimized through established safety guidelines 1
- TMS safety protocols are specifically designed around minimizing seizure risk 1
- No evidence exists of increased serious adverse events causally linked to TMS stimulation in depression treatment 1
Theoretical Concerns in Specific Populations
- Factors that independently increase seizure risk (such as recent substance use, alcohol withdrawal, or concurrent use of medications that lower seizure threshold like bupropion) could theoretically increase sensitivity to TMS-induced seizures 1
- Increased vigilance is warranted when theoretical concerns exist, though standard TMS safety guidelines have not required adjustment for depression treatment 1
Safety Profile Compared to Alternatives
Advantages Over Pharmacotherapy
- No systemic side effects unlike antidepressant medications 3
- No drug-drug interactions, making it particularly valuable for patients on multiple medications 3
- Lower risk of serious adverse events compared to SSRIs 7
- Better tolerability with fewer side effects than standard antidepressants 7
Safety in Special Populations
- Elderly patients with depression experience rare, mild, and transient adverse effects, supporting TMS as a safe alternative when medication side effects or comorbidities are limiting 2
- Pharmacological co-treatment is not essential for clinical improvement, highlighting TMS's safety as a standalone therapy 2
Clinical Monitoring Recommendations
Standard Safety Measures
- Rigorous training of TMS administrators is essential to ensure quality technical procedures, guarantee patient safety, and maximize benefits 1
- Clear documentation of stimulation parameters (location, coil type, frequency, intensity, number of sessions) should be maintained 1
- Any risk factors that apply to the general population (presence of implants, skull defects) similarly apply in depression treatment 1
Minimizing Cognitive Side Effects
- Use lower frequencies (≤5 Hz) when possible, as frequencies of 10-20 Hz have higher likelihood of causing temporary cognitive disruption 5
- Consider longer intervals between pulse trains to minimize interruption of cognitive task accuracy 5
- Inform patients about the possibility of experiencing temporary memory difficulties during treatment sessions 5
Treatment Discontinuation
- Discontinuation due to side effects is uncommon and should not be considered treatment failure if it occurs before completing 4 weeks without clear evidence of non-response 1
- The difficulty in retrospectively distinguishing between non-response and intolerance supports continuing treatment when tolerable 1