Genetic testing for use in psychiatry is a developing science and a useful technique that I like to use in my practice when appropriate.
First let’s talk about what this sort of genetic testing cannot do. It cannot diagnose a mental health disorder. While there are indications that certain genetic variations might be correlated with a mental disorder, there is not sufficient evidence to allow us to make a diagnosis based on genetics alone. Psychiatric diagnosis still requires a clinical evaluation. Also, as with many things, having a genetic tendency to develop a certain mental or medical condition does not mean that you are destined to develop it. There are usually environmental exposures or stressors that can trigger the development of the condition. Another thing that this sort of genetic testing cannot do is to definitively determine what is the best medication for you, although it can certainly give guidance on which medications are best based on your genetics.
The genetic test I use in my practice looks at both pharmacodynamic and pharmacokinetic genes. Those are big words! Let me explain both of these concepts a little further.
Pharmacodynamics has to do with how a particular medication will affect your body. For example, a particular antidepressant can interact with certain receptors in your brain, and this causes a certain response. In short, pharmacodynamics has to do with how your body responds to a medication. The genetic test looks at certain genes that are relevant to how you will react to certain psychiatric medications. For example, some people have a variation in a gene commonly referred to as the serotonin transporter gene. Serotonin is a neurotransmitter (a neurotransmitter is a chemical used in your brain for neurons to communicate with one another) that is frequently the target of antidepressant medications, and increasing serotonin appears to help with symptoms of depression. Some variations in the serotonin transporter gene can predict a poorer response to certain antidepressant medications, and those people may also be more likely to experience side effects from those medications. Knowing whether the patient has this variation in the serotonin transporter gene can be very helpful because then we can choose a medication the patient it more likely to respond to at the very start.
Pharmacokinetics has to do with how your body metabolizes a medication. Every time you take a medication your body has to metabolize it and excrete it. Most often the drug is metabolized by certain enzymes in your liver. People have genetic variations in their liver enzymes and the genetic test will detect your particular profile of liver enzymes used to metabolize medications. Because of these genetic variations, various medications might be metabolized more slowly or more quickly in different people. This means that some medications should be dosed lower in some people who are shown to metabolize that drug more slowly, and also means some medications might need to be dosed a little higher in people who will metabolize the drug more quickly. Having this information from the genetic test can be quite helpful in managing your medications.
The bottom line is that genetic testing can be a useful tool, but psychiatric medication management is still not a precise science, and requires clinical diagnosis and adjustments depending on response. It is also important to note that just because the genetic test finds that a particular medication might be a good option for you based on your genetics, it does not mean you need that medication! For example, if your genetic test finds no problems with prescribing a stimulant to you based on your genetic profile, you should not be prescribed a stimulant medication for ADHD if you do not have ADHD.
I hope this information has been helpful and welcome any questions you may have!