Pharmacogenomic testing: promising treatment for depression

The World Health Organization predicts that depression will be the leading cause of disability worldwide by 2030.

Pharmacogenomic testing of adults with moderate or severe major depressive disorder (MDD) shows promise in helping select the right antidepressant, which could save health systems millions of dollars and improve survival and quality of life, according to a study from that province published in CMAJ (Canadian Medical Association Journal).

“Major depressive disorder is common, recurrent and a large driver of health care costs and burdens in Canada and other jurisdictions that is increasing, especially since the COVID-19 pandemic,” writes Dr. Shahzad Ghanbarian, Vancouver Coastal Health Research Institute, and The School of Public and Population Health, University of British Columbia (UBC), Vancouver, BC, with coauthors.

The World Health Organization predicts that depression will be the leading cause of disability worldwide by 2030. However, only about 40–60 per cent of patients respond to the first antidepressant prescribed, and as much as 42 per cent of variation in response to these medications relates to genetic factors that affect medication metabolism. 

“Pharmacogenomic testing, therefore, is theoretically compelling; using a blood, saliva or buccal swab sample, the test identifies genetic variants involved in drug metabolism and response, which can guide prescribing,” the authors write. 

In close collaboration with patient partners, clinicians and other stakeholders, researchers developed a microsimulation model to evaluate the effectiveness and cost-effectiveness of pharmacogenomic testing for patients with MDD in British Columbia (BC). The model simulated a population of 194 149 people based on administrative data and incorporated 40 different antidepressants as well as other treatments, such as electroconvulsive therapy (ECT) and psychotherapy. They compared treatment pathways for people with and without pharmacogenomic testing over a 20-year period.

Pharmacogenomic-guided treatment resulted in 23 216 (37%) fewer patients developing refractory depression, a key driver of health system cost-savings, as well as fewer patients using ECT and psychotherapy. This would save the BC health system $956 million over 20 years, according to the model.

“The availability of pharmacogenomic testing resulted in patients spending 15 per cent more time in the well state and 18 per cent less time in the MDD state (recurrent episodes or refractory depression),” write the authors, who added that this would mean 1869 fewer deaths and 21 346 fewer all-cause hospital admissions over 20 years. 

“The analyses presented here point toward pharmacogenomic testing, focused on adults with moderate-to-severe MDD, offering the opportunity for a major value-promoting investment by health systems. Pharmacogenomic testing, focused in this way, has the potential both to reduce costs and improve health outcomes,” the authors conclude. 

“Cost-effectiveness of pharmacogenomic-guided treatment for major depression”  was published November 14, 2023.