Major depressive disorder remains one of the most common and disabling psychiatric conditions worldwide. While antidepressant medications help many patients, a significant portion do not achieve meaningful relief. This treatment resistance has fueled growing interest in noninvasive brain stimulation approaches such as transcranial magnetic stimulation. Even with TMS, however, not all patients respond, highlighting the need for better ways to match the right treatment to the right person.
Recent research suggests that EEG biomarkers may offer a path toward more personalized and effective TMS treatment. By measuring brain activity before treatment begins, clinicians may be able to predict who is most likely to benefit and how stimulation should be delivered.
Why Precision Matters In TMS For Depression
Standard TMS protocols often target the same brain regions using similar stimulation parameters for most patients. While this approach is practical, it does not account for individual differences in brain function. Depression is a biologically diverse condition, and patients may have different patterns of neural activity driving their symptoms.
Precision medicine aims to tailor treatment based on measurable biological signals. In psychiatry, EEG provides a noninvasive and relatively accessible way to capture real time information about brain function. When combined with TMS, EEG may help move depression care away from trial and error and toward more data driven decision making.
Key EEG Biomarkers Linked To TMS Response
Studies examining EEG biomarkers in depression have identified several patterns that appear relevant for predicting response to noninvasive brain stimulation. Resting state EEG has shown that differences in spectral power, particularly in alpha and theta frequency bands, may be associated with symptom severity and treatment outcomes. Frontal alpha asymmetry, a measure of balance between left and right frontal brain activity, has also been linked to mood regulation and antidepressant response.
Connectivity measures derived from EEG provide insight into how different brain regions communicate. Disrupted connectivity patterns are common in depression and may influence how the brain responds to stimulation. Identifying these patterns before treatment could help clinicians adjust targets or protocols accordingly.
What TMS EEG Adds To Personalization
Beyond resting EEG, combined TMS EEG offers a more direct way to assess brain responsiveness. By delivering magnetic pulses and recording the brain’s immediate electrical response, researchers can measure cortical excitability and inhibition. Specific TMS evoked potentials, such as the N100 and N45 components, have been associated with treatment outcomes in patients with major depressive disorder.
These signals reflect underlying neurotransmitter activity and network function. If a patient’s brain shows a particular response profile before treatment, clinicians may be able to fine tune stimulation intensity, frequency, or target location to maximize benefit.
Challenges To Clinical Implementation
Despite promising findings, EEG guided TMS is not yet routine clinical practice. Many studies involve modest sample sizes and use different stimulation protocols, making it difficult to establish universal standards. Technical expertise and equipment requirements also vary across clinics, which can limit scalability.
However, as methodologies become more standardized and evidence continues to accumulate, EEG biomarkers are increasingly viewed as a practical tool rather than a purely research focused measure. Integration with neuronavigation systems and other innovative modalities may further enhance feasibility in real world settings.
What This Means For Patients And Clinics
For patients, EEG guided TMS could mean shorter treatment courses, fewer ineffective sessions, and higher chances of meaningful improvement. For clinics, it represents a step toward mechanism based care that aligns with broader trends in precision psychiatry.
As research continues to refine which EEG biomarkers matter most, noninvasive brain stimulation for depression may become more targeted, efficient, and effective. EEG does not replace clinical judgment, but it may soon play a central role in guiding how TMS is delivered.
Citations
- Romero-Marín R, Cappon D, Solana-Sánchez J, et al. EEG biomarkers for a precision-medicine approach to noninvasive brain stimulation for major depressive disorder. Psychiatry Research Neuroimaging. 2025; DOI:10.1016/j.pscychresns.2025.112121. https://pubmed.ncbi.nlm.nih.gov/41483580/
- O’Reardon JP, Solvason HB, Janicak PG, et al. Efficacy and safety of transcranial magnetic stimulation in the acute treatment of major depression: a multisite randomized controlled trial. Biological Psychiatry. 2007;62(11):1208–1216. https://pubmed.ncbi.nlm.nih.gov/17573044/