As we discussed previously, a genetic predisposition to a disease means that a person has genetic factors that contribute to an increased risk to develop the disease but does not directly cause the disease. We reviewed several categories of types of diseases based on etiology that can genetically predispose a person to a disease. Many people wonder, is depression a genetic disease? Am I at risk for depression if I have family members with depression?
More than 19 million American adolescents and adults are affected by depression. This condition is about twice as common in women as in men. Due to the complexity of causes of depression, it is difficult to determine the exact genetic cause. We know that depression is a multi-factorial condition, or caused by a combination of genetics and environment, but we are still trying to identify the genetic components. In order to do so, scientists first started with studies to determine if depression has a heritability component, or roughly what percentage of depression is caused by genes compared to the environment. Twin studies and family studies show that the heritability component is about 37% for depression, and that first-degree relatives of individuals diagnosed with depression have a two to three-fold increase to have depression above the general population. While we know that there clearly are genetic components, depression is not as simple as some diseases that have a clear single gene that causes the disease.
The first study that attempted to find the possible genes associated with depression was published in 1978. Since then, more than 100 genes have been identified that could be associated with depression or symptoms related to depression. Some of those genes thought to be associated with depression may have a role in the production, transport, and activity of chemicals called neurotransmitters in the brain. Neurotransmitters relay chemical signals that let nerve cells communicate with each other. Other genes thought to be associated with depression play a role in the growth, maturation, and maintenance of the nerve cells.
Many will want to know which environmental factors affect your risk of depression. It’s hard to pinpoint exactly which factors, but some could include severe childhood physical or sexual abuse, childhood emotional and physical neglect, severe life stress, or losing a parent early in life. There are most likely many more factors that we have not researched yet that contribute to an increased risk of depression.
Currently we do not have great genetic tests to identify the genes associated with depression, because we are still in the process of researching those genes. However, there are clinical genetic tests being offered to help guide treatment for depression. If you have a diagnosis of depression and are struggling to find a medication that works for you, your provider may order a genetic test that looks at your genetic instructions to better determine which medication you would respond to and help alleviate your symptoms of depression.
If you have a family history of depression, you most likely have a genetic predisposition to depression. If you have a personal history of depression, any future posterity will also have an increased risk to have depression. If you are concerned about your risks and would like to speak with a genetic counselor, please contact AT-GC to schedule an appointment.
Shadrina, M., Bondarenko, E.A., Slominsky, P.A. Genetics Factors in Major Depression Disease. 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6065213/