Exploring the Role of Genetics, Pharmacogenomic Testing in Psychiatric Disorders

Genetics are increasingly playing a role in various aspects of healthcare, and mood and psychiatric disorders are no exception. The American Journal of Managed Care^® (AJMC^®) recently spoke with John Nurnberger, MD, PhD, distinguished professor of psychiatry at Indiana University School of Medicine, about the importance of genetic screening of patients with psychiatric disorders, as well as the importance of pharmacogenomic testing to support treatment decisions.

AJMC^®: How important are genetics in mood and psychotic disorders, and are there certain disorders in which genetics plays a larger role?

Nurnberger: Genetics are important in all the major psychiatric disorders. It’s probably most important in bipolar disorder, schizophrenia, and autism spectrum disorders.

AJMC®: Have you found that there’s enough of an emphasis placed on genetics in these disorders?

Nurnberger: No—I’ll tell you why I say that. I think people have been aware for years that there is a role of genetics in these disorders, but it’s been perceived as a fact that doesn’t really enter into clinical management or treatment very much. So, I think that the point of my presentation today was to say yes, there are implications for treatment and management and that it’s important for psychiatrists and psychiatrists in training to know about genetics and know what those implications are.

AJMC^®: How important is pharmacogenomic testing to support treatment decisions and making sure patients are getting the right treatment?

Nurnberger: That’s part of it. I will say that I try to emphasize that it’s important for people to have skepticism of the results of the pharmacogenomic tests and not to just take it as a given that the results are accurate, because there’s many different testing companies out there. The testing results don’t always agree.

The testing is based on algorithms that are not obvious to the user and there’s a combination of very useful information and information that’s not so useful. So, I think that the evidence is growing that pharmacogenomic testing is valuable in some circumstances, and we still have a lot more work to do to understand what it is that’s valuable and how valuable is it and how it should be used.

I recommend that people consider pharmacogenomic testing before starting carbamazepine oxcarbazepine because of the risk of Stevens-Johnson syndrome and the testing that should be done is HLA testing. And then I also recommend that people consider pharmacogenomic testing for people that have failed multiple antidepressants and that they mainly look at the results of specific enzymes—2D6 and 2CNT—in making treatment choices. Those are the recommendation of the International Society of Psychiatric Genetics, which I belong to and the information is on their website.

AJMC^®: What are some emerging areas in regard to genetics that we’ll see over the next few years?

Nurnberger: There’s a couple of areas there. One is that right now, the chromosomal microarray is recommended for people with autism spectrum disorders, but I think increasingly, it’s going to be useful to use exome sequencing, specifically sequencing of specific targeted genes in assessment of autism. The other thing is that there is this method called polygenic risk score calculation that is now being employed in many medical disorder, including psychiatric disorders, and it is capable of providing specific risk estimates for various disorders, including psychiatric disorders. The risk estimates are not yet precise enough to use in clinical practice, but they will be because the sample sizes are growing from which these estimates are derived, and I expect they will be critically useful within the next 10 years.

AJMC^®: Do you think it’s important to make sure that not just psychiatrists have an understanding of genetics, but also psychiatric residents?

Nurnberger: We think it’s really important for psychiatric residents to be exposed to genetics during their training and one of the main reasons is that their patients are going to increasingly be asking them questions that require an understanding of genetics in order to give a proper answer, and not only that; patients are increasingly bringing genetic test results to their doctors and asking for help in interpreting them. So, we think this is really important, particularly for psychiatrists in training, but I would say it’s important for psychiatrists in practice to become more knowledgeable, as well.