More of my patients now arrive with a pharmacogenetic report, an ad promising to “end trial and error,” or an MTHFR result from an online forum. Others ask for a blood test or brain scan to “prove” their depression. These requests are reasonable. Patients want objective answers to a frustrating process. But the marketing has run ahead of the evidence, and the conversation increasingly falls to us. Here is how I frame it.
What pharmacogenetic testing can and cannot do
Pharmacogenetic (PGx) panels mostly assess liver enzyme genes, chiefly CYP2D6 and CYP2C19, that metabolize many antidepressants. Results can identify poor metabolizers, who are prone to side effects and may need lower doses. They can also identify rapid metabolizers, in whom a drug may not reach adequate levels and who may need a higher dose or a different agent.
What the test cannot do is predict whether a medicine will relieve depression. Response depends on biology, life circumstances, stress, sleep, comorbidities, and other medications. Researchers have searched for genes that predict who responds to a particular drug. Nothing reliable enough for routine use has emerged. The “ends trial-and-error” claim goes further than the data:
- In large studies, guided treatment produced modest gains on some measures. Somewhat more patients reached remission, and some improved sooner.
- The benefit was small and inconsistent. In the GUIDED trial, overall symptom scores, the primary outcome, did not differ between tested and usual-care patients.
- Over the longer term, usual care often caught up. In the VA’s PRIME Care trial, the remission advantage seen early had faded by 24 weeks.
- Results change the plan for only a minority, roughly 15 to 20 percent of patients in some studies. For everyone else, the test shows no important gene-drug interaction for the medicine they are taking.
PGx testing can refine a decision. It does not replace the ongoing work of adjusting medications and doses.
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Decoding the color-coded report
Most reports sort drugs into three groups:
- Green (“use as directed”): No important gene-drug interaction was found. This is not a prediction that the drug will work best.
- Yellow (“moderate interaction”): Genotype may alter drug handling, so a dose adjustment or closer monitoring may be warranted.
- Red (“significant interaction”): A larger effect is expected. The drug is not necessarily off-limits, but it may need a different dose, closer monitoring, or a different choice.
Patients need to hear several caveats. The colors describe metabolism, not efficacy. Some drugs land in green only because no genetic marker is known for them. Some genes on these panels, such as serotonin receptor genes, rest on weak evidence. And the report must be weighed with the patient’s history, other medications, and smoking, which induces metabolism of some drugs, as well as with what has helped before. I tell every patient not to stop or switch a medication based on its color without talking to me first.
When testing is worth discussing
Testing makes the most sense in three situations:
- The patient has had intolerable side effects at low doses, or no effect at standard doses, across more than one medication.
- Two or more adequate trials have failed.
- You are considering a drug with genotype-specific dosing guidance. This includes many SSRIs, such as citalopram, escitalopram, and sertraline (CPIC SSRI guideline), and the tricyclics (CPIC TCA guideline).
Results last a lifetime and can later inform dosing of some pain, cardiac, and other medications, so a single test can keep paying off. Expert groups still disagree about routine testing for everyone. The VA/DoD depression guideline found the evidence too limited to recommend for or against it.
MTHFR is not an explanation for depression
Common MTHFR variants are very common in the general population. Some studies link certain variants to slightly higher depression risk, and others find no association. A variant does not cause or diagnose depression. Nor is there strong enough evidence that the result should change treatment, and the American College of Medical Genetics and Genomics advises against routine MTHFR testing. Small trials of L-methylfolate show mixed results. If folate is the question, serum folate and B12 levels are more useful, and many of us already check them.
No blood test diagnoses depression, but blood work still matters
Depression and anxiety remain clinical diagnoses, built on a careful history and often supported by the PHQ-9 and GAD-7. Inflammatory and stress-related biomarkers are under study, but none is accurate enough for routine use. Patients should be wary of companies selling diagnostic blood tests. What blood work does is look for medical contributors and keep treatment safe:
- Thyroid function, since hypothyroidism can mimic depression and hyperthyroidism can mimic anxiety
- A complete blood count, to check for anemia as a cause of fatigue and low energy
- A basic metabolic panel, covering kidney function, glucose, and electrolytes
- B12 and folate levels
- Liver tests, a drug screen, testosterone in men, or HIV and syphilis testing when relevant
Treating an underlying condition can improve mood substantially. Lithium, some mood stabilizers, and some antipsychotics also require monitoring of drug levels, kidney and thyroid function, glucose, or lipids.
Brain scans: research tool, not clinical test
Group-level MRI and PET studies show differences in people with depression, but the differences are too small and variable to diagnose an individual. Some models predict treatment response well in their original sample and then fail in new groups of patients, a pattern documented across psychiatric prediction research. Clinics that advertise scans to diagnose depression or choose medications are going beyond the current evidence. Imaging earns its place when something doesn’t fit the typical picture:
- Abnormal neurological signs, such as weakness, numbness, trouble speaking, vision changes, seizures, or a new severe headache
- Cognitive decline, or depression that starts for the first time later in life
- First-episode psychosis (some guidelines recommend MRI for everyone, while others recommend it only when the history or exam is concerning)
- A recent head injury, or a sudden change in personality
- An atypical course, or symptoms not improving as expected, when inflammation or infection in the brain is suspected
For typical depression or anxiety with a normal exam, a scan rarely helps and can turn up incidental findings that lead to worry and more testing.
Cost and privacy
Coverage for PGx testing varies. Medicare, Medicaid, and many private insurers cover it in certain situations, often after one or more medication trials have failed. Patients should confirm their out-of-pocket cost first, since some tests cost several hundred dollars or more.
Privacy deserves a conversation, too. The Genetic Information Nondiscrimination Act (GINA) bars health insurers and employers with 15 or more employees from using genetic information against people. It does not cover life, disability, or long-term care insurance, though a few states add protections. Patients for whom that matters may want those policies in place before testing.
The conversation we owe patients
Patients are not wrong to want objective tools. Our job is to explain clearly what each test can do, what it cannot, and when it is worth ordering. The answer, for now, is that careful assessment, measurement over time, and thoughtful adjustment still do most of the work.
Ravi Singareddy is the founder and medical director of Empower Psychiatry & Sleep in north metro Atlanta, where he leads an interventional psychiatry practice offering transcranial magnetic stimulation (TMS) and Spravato (esketamine) for treatment-resistant depression. Double board-certified in psychiatry and sleep medicine, he brings more than two decades of clinical and academic experience to patients who haven’t found relief with medications alone. He is affiliated with Emory Healthcare.
His interest in neuromodulation dates back to his years as associate professor of psychiatry at Penn State College of Medicine. There, he taught annually on vagus nerve stimulation and novel depression therapies, and he published on long-term combined electroconvulsive therapy and vagus nerve stimulation in the American Journal of Psychiatry. He has authored numerous peer-reviewed papers on sleep disorders, insomnia, anxiety, and depression, with work appearing in Sleep, the Journal of Clinical Sleep Medicine, and Psychiatry Research.
Singareddy is a Fellow of the American Psychiatric Association and the American Academy of Sleep Medicine and practices measurement-based care, tracking outcomes to guide every treatment decision. He shares updates on Instagram.
