What researchers know about the biology of dysthymia comes through the study of the biology of depression.
One area of research is neurotransmitters, which are chemicals found in the brain that help send messages between nerve cells (neurons). An imbalance in certain neurotransmitters may lead to dysthymia disorder.
Three neurotransmitters possibly involved in dysthymia symptoms are serotonin, norepinephrine and dopamine. Of particular interest is an imbalance in serotonin, a neurotransmitter that regulates mood, emotions and other bodily functions. One of the main types of medications used to relieve dysthymia disorder is a selective serotonin reuptake inhibitor (SSRI). SSRIs help increase the available serotonin by blocking its reabsorption.
Although depression is often explained as a chemical imbalance in the brain, Harvard Health Publications reports that researchers now believe other brain-related factors may be just as important as neurotransmitter levels, including:
- Connections between nerve cells
- Growth of nerve cells
- How nerve circuits function.
Brain research also indicates involvement of the limbic system, a part of the brain that regulates activities like emotions, the stress response and physical and sexual drives. Research has identified differences in two parts of the limbic system:
- Activity in the amygdala is higher in a depressed person. Emotionally-charged memories activate the amygdala.
- The hippocampus is smaller in some depressed people. The hippocampus helps process long-term memories.
Researchers are still determining the significance of these brain differences in the biology of dysthymia.
Researchers are also looking at the role of the stress response and its related hormones in the biology of dysthymia. When a person is under stress, the body releases hormones that prepare the body for the “fight or flight” response, that is, getting the body ready to fight or flee from the approaching threat. Once the threat has passed, hormones return to normal levels.
In the modern world, however, many people live in a continual state of stress and hormone levels can become all out of whack. These stressors may include loss or abuse as a child, or trauma or prolonged grief as an adult.
Depression tends to run in families, and researchers have identified some genes that appear to contribute to dysthymia symptoms. That being said, most researchers believe that no one gene is responsible for dysthymia disorder, and that various genes in combination with other factors contribute to the biology of dysthymia.
Harvard Medical School Staff. (n.d.). What causes depression? Retrieved May 26, 2010, from the Harvard Health Publications website: www.health.harvard.edu/newsweek/what-causes-depression.htm.
Mayo Clinic Staff. (2008). Video: Antidepressants Ã‘ How they help relieve depression. Retrieved May 26, 2010, from the Mayo Clinic website: www.mayoclinic.com/health/antidepressants/mm00660.
Price, P. (2004). Biological causes of depression. Retrieved May 24, 2010, from the All About Depression website: www.allaboutdepression.com/cau_02.html.