Depression and Genetics
The genetics of depression are complex. Scientists know that depression can run in families, and that a person’s risk of depression increases if close relatives (such as a parent) also have the disease. Depression in family members, however, does not automatically mean that a person will develop the disease. Instead, a complex mix of heredity, environmental factors and life experiences influences depression onset.
Depression in Family Members
According to the Stanford School of Medicine, having a parent or sibling with depression increases a person’s risk of depression from 10 percent (the average risk of depression in the general population) to 20 to 30 percent.
Studies of identical twins reveal the complexity of the genetics of depression. Identical twins share the same genetic makeup. Presuming the cause of depression was wholly genetic, if one twin developed depression, the other should also develop the disease.
However, this does not always occur. It is possible for one twin to suffer from depression while the other does not. As both twins share the same genetic makeup, they both have the same genetic risk of depression. Some other factor must act as a catalyst for depression onset.
Lifestyle, Genetics and Depression
While depression in family history increases a person’s risk of the disease, other factors are also involved. Genetic makeup may predispose people to depression, so they are more likely to develop the disease when confronted with stress or certain environmental factors.
Family dynamics also complicate the study of genetics and depression. Families may share similar lifestyles and behavioral patterns, which can contribute to depression. These factors could be mistaken for genetic causes. A genetic predisposition to depression, however, could also influence family behavioral trends.
The Search for the Depression Gene
The study of genetics and depression includes attempts to identify specific genes responsible for depression. The discovery of a “depression gene” would revolutionize diagnostic tests and depression treatment.
However, it’s highly unlikely that depression stems from a single gene. While some diseases can be traced to one defective gene, the causes of many conditions are more complex. A disease is often influenced by multiple genes, as well as environmental and lifestyle factors, and this seems to be the case with depression.
At present, the genetics of depression suggest that multiple genes influence mental health. While some of these genes may directly cause depression, it seems more likely that a genetic predisposition for depression makes people more vulnerable to external triggers like stress, trauma or abuse. This predisposition explains why one identical twin, exposed to one set of experiences, can develop depression, while the other twin, exposed to different stimuli, avoids the disease.
Resources
Health Communities Staff. (2007). Depression causes and risk factors. Retrieved May 3, 2010, from the Health Communities website: www.mentalhealthchannel.net/depression/causes.shtml.
Intelihealth Staff. (2010). The role of genes, brain function and mood in depression. Retrieved May 3, 2010, from the Intelihealth Staff website: www.intelihealth.com/IH/ihtIH/WSIHW000/8596/35215/362806.html?d=dmtContent.
Levinson, D., Nichols, W. (n.d.). Major depression and genetics. Retrieved May 3, 2010, from the Stanford School of Medicine website: depressiongenetics.stanford.edu/mddandgenes.html.
University of Maryland Medical Center Staff. (n.d.). Depression – causes. Retrieved May 3, 2010, from the University of Maryland Medical Center website: www.umm.edu/patiented/articles/what_causes_depression_000008_2.htm.