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Genetic Factor of Major Depressive Disorder

Major depressive disorder is a psychiatric condition in which the patient feels an all-encompassing feeling of low self-worth. Symptoms include insomnia, persistent low mood, a lack of interest in everyday activities and an inability to feel pleasure. Major depressive disorder is twice as likely to occur in women as men. Major depressive disorder is most effectively treated both with prescription medication and psychiatric therapy.

  1. Physiology of Depression

    • While the causes of depression are not completely understood, there are certain noticeable differences in the brains of people who suffer from depression. The primary difference is a noticeable lack of certain neurotransmitters called catecholamines. These catecholamines are commonly responsible for activating the "reward" centers of the brain, and include the neurotransmitter serotonin.

    Depression and Twins

    • If one of a set of identical twins has major depressive disorder, there is a 50 percent chance that the other twin will also be afflicted with major depressive disorder. For nonidentical twins (also known as dizygotic twins), there is a similar link, though smaller (35 percent). This suggests that there is a certain genetic component to major depressive disorder.

    Depression and Parents

    • Other studies, looking at the incidence of depression in children with parents who suffer from major depressive disorder, have found a similar link. In the 1970s, Dr. Myrna Weissman began a longitudinal study while at Yale that in 2009 has identified heritable changes in brain structure that can put a person at risk for major depressive disorder. Overall, there appears to be a 39 percent correlation between parents and children who suffer from depression. These studies, however, do have trouble differentiating between genetic factors and the influence of living with parents who suffer from depression as they relate to the likelihood of experiencing major depressive disorder.

    Chemical Receptors

    • In 2008, researchers at the University of Michigan found that there is a link between the abundance of certain chemical receptors in the brain and the severity of depression. Specifically, when there is a lack of certain proteins that bind to serotonin and other neurotransmitters, it is more likely that the affected person will suffer from depression. It has also been found that patients with this genetic abnormality do not respond as well to antidepressants.

    Epigenetics

    • Another aspect of the genetic factors behind major depressive disorder is called epigenetics. Epigenetics does not refer to mutations within genes, but rather modifications that alter how the body responds to these genes. Genes can be chemically altered in various ways. One such method, called methylation, involves the attachment of a very small molecule made out of carbon and hydrogen to the DNA. This causes some of the proteins that use DNA to ignore that particular gene. Other genes can be modified epigenetically by storing them away in proteins where they are inacessible to the rest of the cell. These modifications can be just as important as inherited genetic characteristics. As a result, genetic changes that aren't hereditary have also been found to be linked to major depressive disorder.

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