Everything you need to know about TMS and Genetics: Will Your DNA Predict Your Response? — how it works, what it costs, and how to find a provider who actually knows what they're doing.

One of the persistent challenges in TMS is the 40-50% non-response rate. We cannot yet predict with precision who will respond, which has made TMS partly a trial. Genetics is beginning to change this picture — not by giving a definitive answer, but by identifying biological factors that influence response.

The field is called pharmacogenomics, and while it is most developed for medication response prediction, researchers have begun applying its methods to TMS. The early results are interesting enough that some clinics are already incorporating genetic testing into treatment planning.

What You’ll Learn

• Which genetic variants, particularly BDNF Val66Met, predict TMS response
• How polygenic risk scores may personalize TMS treatment planning in the future
• Current clinical use of genetic testing for TMS treatment decisions
• The difference between genetic prediction and full response prediction models
• Practical implications of being a Met carrier for your TMS treatment

What We Know About the Genetics of TMS Response

TMS response has a heritable component. Studies of twins and family cohorts suggest that 20-30% of the variance in TMS response is attributable to genetic factors — not deterministic, but meaningful enough to be detectable.

This is not surprising given what TMS does: it triggers neuroplasticity. Neuroplasticity is itself influenced by genetic factors that regulate synaptic function, neurotrophic support, and neural excitability. Variation in these genes affects how effectively the brain rewires in response to stimulation.

The BDNF Val66Met Polymorphism: The Best-Studied Gene

Brain-derived neurotrophic factor (BDNF) is the neurotrophin most directly implicated in TMS mechanism. BDNF supports synaptic plasticity, and its release in response to TMS is thought to mediate the lasting effects of treatment.

The BDNF Val66Met polymorphism (rs6265) is the single most studied genetic variant in TMS research. The polymorphism affects the efficiency of BDNF trafficking and activity-dependent secretion. Individuals with the Met allele (particularly Met/Met homozygotes) show:

• Lower baseline BDNF levels
• Reduced activity-dependent BDNF release
• Weaker neuroplastic responses to stimulation

Studies consistently find that Val/Val individuals show better response to TMS than Met allele carriers. A meta-analysis published in Translational Psychiatry found that Val/Val carriers had approximately 1.5 times higher odds of responding to TMS compared to Met carriers.

The practical implication: if you are a Met carrier, you may need more sessions, higher intensity, or additional interventions to achieve equivalent results to Val/Val individuals. This is not a reason to avoid TMS, but it is useful information for treatment planning.

Other Genes Implicated in TMS Response

Beyond BDNF, research has identified several other genetic factors:

SLC6A4 (serotonin transporter gene): The s-allele of SLC6A4 is associated with reduced serotonin transporter expression and has been linked in some studies to poorer TMS response. The evidence is mixed — other studies have not replicated this finding — but it remains one of the most investigated variants.

COMT (catechol-O-methyltransferase): COMT metabolizes dopamine in the prefrontal cortex. The Val158Met polymorphism affects dopamine availability in the DLPFC. Some studies suggest Val/Val individuals (who have lower prefrontal dopamine) respond better to TMS, possibly because TMS increases dopamine release in the target region.

GRM7 (metabotropic glutamate receptor 7): A 2023 study found that variants in GRM7 were associated with TMS response in a large cohort. The glutamate system is directly involved in plasticity mechanisms, so this finding is mechanistically plausible.

Neuroimmune genes: Some research has begun exploring whether immune-related genes (IL1B, CRP) affect TMS response, given the growing literature on neuroinflammation in depression.

Current Clinical Use: Genetic Testing for TMS

Genetic testing for TMS planning is not yet standard practice, but some clinics offer it. The commercially available tests that are relevant include:

Psychiatric pharmacogenomic panels (Genecept, GeneSight, Millenna Health) — these tests examine genes related to medication metabolism and response. They may include BDNF variants. While designed for medication selection, the results can inform TMS clinicians about neuroplasticity-relevant biology.

BDNF-specific testing — some labs offer BDNF genotyping specifically. If you are curious about your BDNF status, this can be ordered through your doctor.

Whole exome or genome sequencing — comprehensive genetic testing, rarely used clinically for TMS planning but available for research contexts.

The practical value of current genetic testing for TMS is limited primarily to BDNF. Knowing your BDNF genotype tells you something about expected response magnitude, but it does not change the treatment recommendation (try TMS vs. not try TMS) for most patients. The information is most useful for setting expectations and planning session count.

The Future: Polygenic Risk Scores

The future of TMS pharmacogenomics is polygenic risk scores (PRS) — combining the effects of thousands of genetic variants into a single predictive score. PRS for depression, neuroplasticity, and TMS response are under development at several academic centers.

The goal is not a single gene, but a composite score that predicts with reasonable accuracy (perhaps 70-80% accuracy) whether a given individual will respond to TMS. This would allow truly personalized treatment planning — matching patients to TMS or alternatives before they commit to a six-week course.

This is not yet clinically available. But the trajectory is clear: genetics will become part of TMS treatment planning within the next 5-10 years.

What Patients Should Know

If you have had TMS testing or genetic testing: Ask your clinician if your results include BDNF or other plasticity-relevant variants. The information may inform your treatment approach.

If you are considering TMS and have concerns about response: Discuss genetic testing options with your doctor. While not definitive, the BDNF information is useful and increasingly available.

If you are a Met carrier: This is not a reason to despair. Many Met carriers respond well to TMS. The effect of the polymorphism is probabilistic, not deterministic. It means you may need more treatment, not that treatment will fail.

If you have multiple family members with depression: Family history of good TMS response may be informative — if your relatives responded, you may be more likely to respond.

Beyond Genetics: The Full Prediction Picture

Genetics is one piece of the response prediction puzzle, but not the whole picture. Brain connectivity (measured by fMRI), clinical features (baseline severity, duration of illness, number of prior failures), and even behavioral factors (sleep quality, exercise) collectively predict response better than genetics alone.

The goal is an integrated prediction model combining all available data — genetic, imaging, clinical, and behavioral — to give patients and clinicians accurate expectations before treatment begins. We are not there yet, but the field is moving toward this vision.

Genetics will not tell you with certainty whether TMS will work for you. But it is beginning to add a meaningful layer of predictive information that will only improve over time.