Some doctors find that genetic testing can help identify antidepressants that are more likely to work for a given patient.

Finding the right antidepressant for a patient is typically achieved through trial and error. Often, multiple different medications are tried before one that works is identified, which can take a toll on patients.

Genetic data is increasingly used to predict the risk a person may face in developing a number of different diseases, such as breast cancer, and the right medications to treat specific forms of some diseases, such as acute leukemia and HIV.

Now some doctors are using genetic data to reduce the number of antidepressants that need to be tried, because the data provides information about which types of these drugs will be most effective.

However, not all doctors believe that current evidence is sufficient to support the use of genetics in the treatment of mental health problems. There are some data that link the existence of certain genes with the way drugs will affect the body, but the definitive evidence to support the claim that better results are obtained for patients is still lacking. 

Genetic testing can be expensive (costing anywhere from $100 to more than $2,000, according to the National Institutes of Health), and, absent strong evidence to support that outcomes are improved across a broad swath of patients, some doctors believe that following standard protocols — that don’t carry such high price tags—is the better way to proceed.

Most genetic tests evaluate genes related to metabolism, which can affect how long a drug is present in the body. They seldom take into account age, diet and other substances in the body, which are also important factors in how drugs are processed.

Some argue, however, that for certain gene–drug combinations, the presence of a specific gene or genes can be the most important factor. Mary V. Relling, co-founder of the Clinical Pharmacogenetics Implementation Consortium, says that in certain cases repeated studies of patients with certain genetic defects respond in certain ways –– such as having more toxicity –– to certain drugs.

Part of the argument over using genetic data to prescribe antidepressants relates to the types of study data that are available. Some believe that establishing a strong relationship between a gene and a drug is sufficient, while others believe it is necessary to show that patients have better outcomes when treatments are selected based on genetic data. 

The U.S. Food and Drug Administration’s Center for Devices and Radiological Health and Center for Drug Evaluation and Research weighed in on the issue in late 2018, publishing a statement warning patients and doctors to be cautious about genetic testing that has not been approved by the FDA, including those that guide the prescribing of antidepressants.

According to the statement, “the relationship between DNA variations and the effectiveness of antidepressant medications has never been established. Moreover, the FDA is aware that health care providers have made changes to patients’ medication based on genetic test results that claim to provide information on the personalized dosage or treatment regimens for some antidepressant medications, which could potentially lead to patient harm.”

 The best conclusion, according to Anthony Rothschild, a professor of psychiatry at the University of Massachusetts Medical School, is to use genetic testing results as one tool in the “depression-treating arsenal, especially in cases where patients have not responded to medication.”