Should Psychiatrists Do Genetic Testing Before Prescribing?

Psychiatrists often start antidepressants based on best guesses. Is there a way to prescribe more confidently to increase the likelihood of starting the right medication the first time?

Personalized medicine involves tailoring medications to the individual based on predictions from genetic testing. Psychopharmacogenomics is how a patient’s genome interacts with psychiatric medications.

“I feel that, although it is new, psychopharmacogenomic testing is a game changer for psychiatry.”

Psychopharmacogenomics is important because depression has a strong genetic component. It’s thought be about 40% genetic and 60% environmental. Research indicates that multiple genes interact with environmental factors (such as relationship breakups, illness, death, social drugs, alcohol or work/life stress) to cause depression.

Psychopharmacogenomic testing is taken using a painless swab from the inside of the cheek. Given COVID-19, the testing kit can be overnighted to the patient’s home so there is no need to go to the doctor’s office. The testing examines approximately 130 mental health medications and how they interact with the individual’s genetic makeup.

Pharmacogenomic testing provides three types of information:

1. Target genes such as the serotonin reuptake gene. This is helpful because if patients have a variant with  low activity, they are unlikely to respond to selective serotonin re-uptake inhibitor (SSRI) drugs such as Prozac, Lexapro or Zoloft. These drugs are commonly used as first-line agents for treating depression.
2. How a patient metabolizes different drugs. If patients are fast metabolizers of e.g., Prozac, it is unlikely to be effective. The body will break it down too rapidly. If patients are slow metabolizers, they are likely to accumulate the drug in the body and risk developing side effects.
3. Metabolism of folic acid (folate), a vitamin. Folic acid is essential for the assembly of brain neurotransmitters such as serotonin and norepinephrine. Psychiatrists use folic acid to boost anti-depressant treatment. If a patient has a “MTHFR” variant that has low activity, the patient can be given methylfolate to bypass the slow step. This avoids taking folic acid in its pure form, which is less likely to work.

Genetic testing can also provide information about drug-drug interactions. In patients on multiple medications, predicting these interactions is vital.

The question that psychiatrists are grappling with right now is should this testing be done on initial assessment to guide treatment selection, avoid dead-end trials and minimize side-effects or only if a patient’s first medication does not work or they develop side effects?

I believe it is helpful to do this testing as early as possible. It increases the likelihood that you are being started on the right medication, the first time. Time is a valuable commodity when patients are suffering from depression and are receiving a medication that can take 3-4 weeks to kick in. Additionally, no-one likes suffering from medication side-effects so it’s preferable if they can be avoided.

Psychopharmacogenomic testing in psychiatry is not without its detractors who argue that the technology is too new and there is too little data to support its efficacy.

I feel that, although it is new, psychopharmacogenomic testing is a game changer for psychiatry. Medicare, Medicaid and United Health Care agree since they now cover this testing. Other insurers are likely to follow.

Gone are the days when psychiatrists dismissed patients for being “sensitive to medications” as part of their anxiety. If a patient is sensitive to a medication, one likely reason is that the patient is a slow metabolizer of that medication.