Medications for the treatment of mental illness and substance abuse have been historically prescribed through a trial-and-error process. Many of the drugs prescribed for mental health conditions can take long periods to begin working or have varied response rates, have adverse side effects (e.g., weight gain, suicidal thoughts, headaches) and sometimes do not work at all (e.g., treatment-resistant depression).
As everyone responds to medications differently, pharmacogenomics (i.e., drug-gene testing) is a relatively new tool that can be used to determine how the body will process and respond to a specific medication based on differences in an individual’s genetic makeup. Pharmacogenetic testing essentially examines the differences in patients’ genetic makeup to determine how they will respond to a specific drug and whether they are more likely to experience adverse side effects.
The genetic variants in the individual’s DNA are examined from a small blood or saliva sample collected from the patient, which is then used by the health care provider to determine which medication the patient will respond to best with the fewest adverse side effects. Thus, pharmacological testing is useful for mental health care providers because it enables them to individualize drug therapy based on their patients’ genetic makeup, leading to greater medication and treatment adherence and a better overall quality of life for individuals affected by mental health and substance abuse problems.
Pharmacogenetic testing and improving depression treatment
A study conducted by Rachel Scott, Pharm.D., and her colleagues, reported that pharmacogenetic testing resulted in significant improvements in symptoms, adverse effects and quality of life over a three-month period in patients with mood and anxiety disorders. The majority (87 percent) of patients were judged by clinicians as improved after testing. In addition, patients reported significantly reduced depression and anxiety during the follow-up assessment.
Variations in the serotonin transporter protein (SLC6A4) have been found to help predict how patients will respond to selective serotonin reuptake inhibitors (SSRIs), medications used for antidepressant treatment. In a meta-analysis of antidepressant pharmacogenetic findings in patients with major depressive disorder (MDD), published in the journal Molecular Psychiatry, researchers from the University of Bologna in Italy and the Kansai Medical University in Japan, found that variations in the serotonin transporter protein (SLC6A4), the human gene-encoding serotonin transporter potentially involved in mood regulation, were associated with poor response and remission rates, and increased side effects associated with antidepressant treatment with SSRIs.
The researchers summarized the results of 90 studies that used pharmacogenetic testing during antidepressant treatment and found that five variants in four genes (SLC6A4, serotonin-1A receptor gene [HTR1A], serotonin-2A receptor gene [HTR2A], tryptophan hydroxylase [TPH1] and brain-derived neurotrophic factor [BDNF]) could potentially impact the way people responded to antidepressant treatment. Future studies examining pharmacogenetic testing for antidepressants could be useful for improving medications for treating depression.
Importance of pharmacogenetic testing
The Federal Drug Administration (FDA) reported that pharmacogenetics is useful for avoiding adverse side effects, optimizing drug dose and determining who will respond to certain medications. Currently, there are a total of 113 drug labels that have been approved by the FDA, including several psychiatric medications. The FDA provides specific drug pharmacogenomic information and actions to be taken based on the biomarker information to be used for scientists who conduct pharmacogenetic testing.
To date, the majority of pharmacogenetic testing has been used for tailoring drug treatments by improving drug selection and dosage. Pharmacogenetic testing is important because these genetic variances account for 20 to 95 percent of a patient’s response to a medication. In the future, the use of pharmacogenetic testing may be utilized to develop new drugs and help improve medication adherence (i.e., the degree to which patients’ behaviors are congruent with the health care provider’s medication recommendations).
Sovereign Health of California utilizes pharmacogenetic testing for choosing the best medications for patients in treatment for substance abuse, mental illness and co-occurring disorders. Patients who receive pharmacogenetic testing receive individualized treatment plans and medications based on their specific needs. For more information on the programs offered at Sovereign Health, please contact our 24/7 helpline to speak to a member of our team.
Written by Amanda Habermann, M.S. clinical psychology, Sovereign Health Group writer