How To Find The Right Treatment For DepressionRuslan Dorfman, PhD, MBA
Finding the right treatment for depression is not easy. Physicians have many medications to choose from, however, they know that only a fraction of patients will respond to any given medication. Thus, they employ a “trial and error” approach where they test a specific medication for a few weeks before moving on to another one. Clinical trials, such as STAR*D, have shown that as many as 70% of patients do not respond to their initial prescribed medication. While the trial and error approach does ultimately treat depression in many cases, the delays are a serious issue. Delays in treatment for depression are believed to lead to nonadherence in an estimated 30-60% of patients. Furthermore, adverse drug reactions (side effects) are the leading cause of death in the U.S. and those linked to the use of antidepressants may lead to psychiatric imbalance, leading to increased risk of suicide, anxiety and manic behaviors. Other common side effects of treatment for depression include dry mouth, constipation, blurred vision, nausea, tremor, insomnia and cardiac disturbance. These adverse reactions stem from the fact that different individuals respond differently to medications and much of these differences can be attributed to our unique genetic background.
How Genetic Testing can improve the treatment for depression
Advances in genetic technologies have tremendous potential to improve the treatment for depression and other mental disorders. Pharmacogenetics is a genetic test that assesses person’s ability to metabolize specific medications. Pharmacogenetic testing prior to taking medications can help to improve accuracy of prescription by determining whether an individual will metabolize a specific medication, as well as guide the starting dosage. This significantly reduces any trial and error time and improves treatment outcomes. Pharmacogenetic testing also improves drug safety and reduces the risk of adverse drug reactions since a patient is not exposed to unnecessary medications at potentially harmful doses. The International Society of Psychiatric Genetics (ISPG) recommends promoting educational programs to improve knowledge of genetic medicine among physicians and mental health professionals.
Pharmacogenetic Testing in Clinics
With the cost of genetic testing rapidly falling, its application in a clinical setting is becoming increasingly popular. The Clinical Pharmacogenetics Implementation Consortium (CPIC) provides guidelines for the implementation of pharmacogenetics in clinical settings and has made recommendations on genetic testing for multiple disorders. Both CPIC and ISPG guidelines highlight genetic variations in the CYP2D6 and CYP2C19 enzymes leads to differences in the metabolism of numerous medications relevant to psychiatry, in particular antidepressants and antipsychotics.
In North America, the benefits of pharmacogenetic testing are being recognized and its application is gaining steam. In the US, many insurance providers cover the cost of pharmacogenetic testing for many classes of medications and the FDA has pharmacogenetic labeling for over 260 different medications. However, reimbursement policies exert a great influence on the adoption of pharmacogenetic tests into clinical practice.
Where to find genetic testing for treatment for depression in Canada
CAMH center in Toronto completed large scale study that demonstrated value of pharmacogenetics-based medication management for people with depression – patients who were on a “mismatched” drug significantly improved when were switched to an antidepressant better suited to person’s DNA. Despite positive clinical studies, including the ICANPIC study, Canada lags behind the US in the utilization of pharmacogenetic testing. Provincial health plans still do not yet cover these tests, but increasing public awareness and pressure are likely to change this. Most insurance companies in Canada offer pharmacogenetic testing such as Pillcheck as part of disability management programs and some health benefit plans also over cover pharmacogenetic testing. Pillcheck is eligible for Health Spending Account reimbursement.
- Herbild, L., et al., Do guidelines recommending pharmacogenetic testing of psychiatric patients affect treatment costs and the use of healthcare services? Scand J Public Health, 2011. 39(2): p. 147-55.
- Herbild, L., M. Bech, and D. Gyrd-Hansen, Estimating the Danish populations’ preferences for pharmacogenetic testing using a discrete choice experiment. The case of treating depression. Value Health, 2009. 12(4): p. 560-7.
- Ventola, C.L., Pharmacogenomics in clinical practice: reality and expectations. P T, 2011. 36(7): p. 412-50.
- Maruf AA et al., Pharmacogenetic Testing Options Relevant to Psychiatry in Canada. Can J Psychiatry. 2020 Feb 1