Genetic Testing: Is it for you?
Many patients in recent years have been inquiring about the possibility of using genetic tests to determine if they truly have a biological mental illness, such as bipolar disorder, major depression or schizophrenia. It is not surprising that people want a test that will help them to understand their vulnerability or the specific genetic components which relate to their illness.
These genetic tests, or “genome scans” can provide useful information to doctors and patients as many disorders do have a genetic component to them. Eventually, they may become an integral part of a formal diagnosis for mental illness. However, when it comes to the genetics of mental illness, today, not enough is known about the gene variations involved to give a complete picture of individual risk factors for mental illness.
Your family history may provide you with the best clues about your risk for developing mental disorders. For example, bipolar disorder and schizophrenia tend to run in families. At this time there is no genetic test that will predict absolutely or tell you if you will develop this mental illness. There is not enough information to tell which gene variations contribute to the expression of these disorders. For now, your family history may be your best indicator. For example, studies indicate that if you have a close relative with a bipolar disorder, you have about a 10% percent chance of developing a mood disorder, such as bipolar disorder or depression.
The prevailing view about mood and brain disorders is that multiple genes each contribute a small effect. Not one gene, but many genes, mutations and variations may be involved. There may be up to 10 or 15 changes in the genome for a given illness. Also, the interaction between genes and environment is very important. A recent study has shown that a short form of a gene codes for a molecule that binds the neurotransmitter serotonin, and if you have early life adversity, and lots of late life stress, you may have a strong likelihood of becoming depressed.
Given the steady progress by scientists and medical researchers, tests for psychiatric and psychological disorders are now emerging. One of the early companies leading in the commercialization of these genetic scan products is called Psynomics. You can find them on the web at http://www.psynomics.com. This company was started by psychiatric genetic scientists from the University of California at San Diego. Psynomics, a company that will test for two mutations found on the GRK3 gene. In research on hundreds of families, one of the mutations appeared in one percent of individuals without the illness and three percent of persons with it. The second mutation showed up in 15% percent of people with bipolar disorder. Again, with so many genes involved in psychiatric disorders, this test may explain only a small percentage of the genetic risk for illness. Nevertheless, it is a very positive early start in the search for understanding the relative risk of bipolar disorder for individuals. The test is marketed to persons with bipolar symptoms and results are sent to their doctor. Once again, the potential for misunderstanding multiple gene disorders is great. Interpreting and understanding the results of these psychiatric genetic tests must be taken with great care. The possibility of misuse, stigma and bias for individual patients must not be taken lightly.
What are Genes?
Genes are pieces of DNA, in cells, that parents pass down to their children at conception. Genes turn on and off throughout life to transmit chemical instructions for making the body’s proteins. Proteins are part of what gives us our characteristics, for example, our height, eye color, personality, and our chances of getting specific diseases.
Genes can have slight differences in their structure from person to person and these variations can cause difference in people’s characteristics. Gene variations help explain why members of the same family often look alike and have other characteristics in common, such as certain illnesses-because each child inherits a mixture of both parents’ gene variations.
Some gene variations make people more vulnerable to different diseases, and some have protective effects against different diseases. Some rare diseases are caused by variations in a single gene. Most common diseases are caused by a mixture of many gene variations, some unknown and external factors, such as stress or toxic substances.
Some gene variations appear to have no effect on risk of disease.
For more information about gene-related research on mental illness, visit the National Institute of Mental Health Web site at http://www.nimh.nih.gov/.
For information about genetics research, visit the National Human Genome Research Institute Web site at http://www.genome.gov/.
Much of this information is provided by The National Institute of Mental Health, Office of Science Policy, Planning and Communications in the manuscript “Looking at My Genes: What Can They Tell Me?”