New genetic testing could tell you which antidepressant works best for you

By Jessica Werb

Here’s how it works, and how it could help treat depression faster

Major depression is debilitating, painful and, unfortunately, common, affecting one in 10 Canadians. And while there are many antidepressant options available, finding one that is effective can involve a lengthy process of trial and error. That may soon change, however, with the rise of pharmacogenomic testing that can provide information about how effective a drug will be, based on a person’s DNA.

More than half of patients do not respond to the antidepressant they are first prescribed, according to Dr. Jehannine Austin, professor of medical genetics and psychiatry, and Dr. Shahzad Ghanbarian, mathematical modeler at the Centre for Clinical Epidemiology and Evaluation at UBC. The University of British Columbia researchers share how pharmacogenomic testing holds the promise of faster, effective treatment—and how to access it.

What is pharmacogenomic testing?

Dr. Austin: Pharmacogenomic testing is about taking a sample of saliva or blood, and looking at the DNA in it for genetic variations that influence how we metabolize the drugs that we might be prescribed. The way that we metabolize medicines is, in part, dictated by our genetics, and everybody’s genetics is a little bit different.

How can pharmacogenomic testing help someone experiencing clinical depression find the right antidepressant for them?

Dr. Austin: It’s not about doing a test and saying, “Aha, this is the one drug that you should use and these are the ones that you should not.” The results that you get would be more along the lines of, “Based on your genetic testing results, these ones would be more likely to work well for you, and these ones would be less likely to work well for you.”

Dr. Ghanbarian: Studies show that 40 to 60 per cent of patients do not respond to the first antidepressant they’re prescribed. And some can go through many trials to get to the effective medication. That’s a frustrating process for the patient and it’s also challenging for the prescribers. If we can find them effective antidepressant faster, we can reduce the number of patients with treatment-resistant depression, and cut costs to the health system, too.

How can Canadians get access to pharmacogenomic testing for antidepressants?

Dr. Ghanbarian: A number of pharmacogenomic tests are available to patients in Canada through some pharmacies, benefits plans, and direct-to-consumer online. Most require a requisition from a healthcare provider. They’re not currently publicly funded, so patients pay out of pocket. They cost from $300 to $2,500, although some may be covered by private insurance. It’s important to work with a healthcare provider in choosing which test to use.

Is pharmacogenomic testing available for other diseases or disorders?

Dr. Austin: Yes. It has been used in oncology and cardiology a lot, and the UK has implemented it for HIV treatment. When it comes to psychiatric conditions, there is the most data about using pharmacogenomics in treating major depression. However, the same principles apply for other conditions that are psychiatric in nature, such as anxiety or schizophrenia. You could use pharmacogenomic testing in the context of those conditions, too. It’s just that we have a lot less data about its effectiveness.

What are the benefits of using pharmacogenomic testing for depression?

Dr. Ghanbarian: We found that the health system in BC alone could save an estimated $956 million over 20 years by providing pharmacogenomic testing for the treatment of moderate to severe major depression. Other provinces could see similar benefits. But there are also bigger savings on a societal level. Patients who have difficulty finding an effective treatment for their symptoms of depression not only deal with having side effects and disappointment. Some of them cannot work, or they lose their jobs, or need someone to take care of them. From an economic perspective, pharmacogenomic testing is a “no-brainer”. Not only does it save the government money, but patients and society also benefit as well. Plus, getting people effective treatment faster will also save lives.

Jessica Werb is a writer for UBC Brand and Marketing. With files from Brett Goldhawk, UBC Faculty of Medicine. This article was published on January 17, 2024. Feel free to republish the text of this article, but please follow our guidelines for attribution and seek any necessary permissions before doing so. Please note that images are not included in this blanket licence.