Smoking status & the GeneSight test
In August 2023, Myriad Genetics enhanced the GeneSight Psychotropic test to include information on how a patient’s smoking status may impact their body’s metabolism of certain mental health medications.
The GeneSight Psychotropic test will now provide non-smoking and smoking results when applicable. These updates were based on a comprehensive analysis of peer-reviewed literature and our continued commitment to provide clinicians and patients with genetic insights to help inform treatment decisions.
The prevalence of smoking cigarettes in patients who have depression or anxiety is higher than in the general population.1 Daily or near-daily use of marijuana is two times higher in individuals with depression compared to those without it.2
What’s considered “smoking”?
On the GeneSight report, smoking is defined as the daily inhalation of burning plant material, such as cigarettes and marijuana. The definition excludes vaping and e-cigarettes.
How does smoking affect my GeneSight test results?
In addition to genetics, environmental factors, such as smoking, can cause a gene-drug-environment interaction, which may affect how certain medications are broken down in the body. The CYP1A2 gene encodes for the CYP1A2 pharmacokinetic enzyme that is involved in the metabolism (or breakdown) of various medications, including certain antidepressants, anxiolytic and hypnotics, and antipsychotics.
Some patients have a highly inducible genetic variant in the CYP1A2 gene, and this variant in the presence of smoking can result in increased CYP1A2 activity. This increase in CYP1A2 activity may result in faster than normal breakdown of certain mental health medications found on the GeneSight report. For these patients, the categorization and information provided on the GeneSight report for certain medications can be affected by smoking status.
See this Genetic Insight for more information on rates of metabolism.
What is the prevalence of the CYP1A2 variant?
Data has shown that about 91% of patients have a CYP1A2 variant that is highly inducible by smoking. The presence of this variant in those who smoke may cause certain medications metabolized by CYP1A2 to be broken down more quickly than normal.
For the roughly nine percent of patients who don’t have the CYP1A2 highly inducible variant, smoking is not expected to impact how quickly these medications are metabolized through CYP1A2.
How many medications are potentially affected by smoking?
Roughly a third of all medications on the GeneSight Psychotropic report are identified as having CYP1A2 involvement. These 23 medications include several antidepressants, anxiolytics and hypnotics, and antipsychotics.
How does smoking status appear on the GeneSight report?
The GeneSight report has been modified to include new labeling about smoking status near the top of the impacted medication pages for patients with the highly inducible CYP1A2 variant (91% of the population). For these patients, the GeneSight report will include non-smoker and smoker pages of results for antidepressants, anxiolytics and hypnotics, and antipsychotics.
In addition, medications impacted by smoking status are labeled with clinical consideration number 7, which indicates that smoking status changes the results of the specific medication. Accordingly, clinicians are referred to use the section labeled “Smokers” if the patient smokes.
Medications in two other classes on the report – mood stabilizers and stimulants and non-stimulants – will not have separate non-smoker and smoker pages, since CYP1A2 is not predicted to influence the breakdown of these medications.
Patients who do not have the highly inducible CYP1A2 variant will not receive separate non-smoker and smoker results. For these patients, their reports will note that the test results provided are for both non-smokers and smokers since the patient does not have the highly inducible CYP1A2 variant.
For more information on how to interpret GeneSight report, please read this Genetic Insight.
How will my clinician use the test results?
Your clinician may use the results of the GeneSight Psychotropic test to help inform medication selection and treatment decisions, based on your unique genetic makeup. Test results could be especially helpful for patients who have experienced side effects or have failed to respond to certain medications.
For more information on the GeneSight test, email us at firstname.lastname@example.org, or call us 855.891.9415.
This document is for educational purposes related to pharmacogenomics and personalized medicine only and should not be considered medical advice. The information is based on scientific opinion from industry experts and is intended to provide additional information to healthcare providers. These materials may be changed, improved, or updated without notice. Myriad Genetics is not responsible for any errors or omissions contained in third-party content. We encourage you to contact us for specific scientific advice regarding our GeneSight® tests. You may print a copy of this document for your own personal noncommercial use. You may not copy any part of this document for any other purpose, and you may not modify any part of this document without the permission of Myriad Genetics. All rights reserved.
1 Cornelius, M.E. et al. (2022). “Tobacco Product Use Among Adults- United States, 2020.” MMWR Morb Mortal Wkly Rep, 71
2 Dai, H. and K.P. Richter. (2019). “A National Survey of Marijuana Use Among US Adults with Medical Conditions.” JAMA Network Open, 2(9):e1911936