The causes of depression continue to elude medical science. While many risk factors for depression are known, none can be considered to actually cause depression. Stressful life events, for instance, are well known risk factors for depressive episodes. But two people exposed to the same stressor can have radically different reactions. One may live through the stressor with no observable negative effect, while the second experiences a major depressive episode. Stress alone does not explain why people suffer from depression—it may trigger the underlying cause of the mental illness, but it does not, by itself, cause depression.
At present the root causes of depression are thought to lie in four areas: genetics, environmental factors, hormonal changes and brain chemistry imbalances.
Genetics: Is Depression a Hereditary Mental Disorder?
Depression and related mood disorders have a strong tendency to run in families, suggesting at least some types of depression are inherited mental disorders.
A person is up to three times more likely to develop depression if he or she has a sibling or parent who experienced depression (when compared to the general population). In studies of identical twins, if one twin received a depression diagnosis the other twin had a risk of depression ranging from 67 to 76 percent higher than the normal rate. Twins who had been raised apart had the lower risk for depression if their sibling was depressed, although their risk was still 67 percent higher than normal.
Such studies make a strong case for genetics as a cause of depression. Genetics alone, however, cannot explain all cases of depression. A person with no family depression history can still develop clinical depression.
Family depression history certainly hints at a genetic cause for some depression cases, but environmental factors may also play a role. Family members tend to share environmental stressors and lifestyles, which may also influence a person’s susceptibility to depression.
Neurochemistry and Depression
Other studies look to the brain itself for the cause of depression. Brain imaging technology reveals some interesting changes in the brains of depressed people.
When compared to brains of people who are not depressed, a depressed person’s brain shows a number of abnormalities. Areas of the brain affected by depression include areas that regulate:
- appetite
- behavior
- cognitive functioning
- mood
- sleep patterns.
All of these mental processes are significantly impaired or disrupted by clinical depression.
Depression alters brain chemistry. Neurotransmitters are vital brain chemicals that allow messages to travel from one brain cell to another. Depression alters the brain’s neurotransmitter levels, resulting in imbalances that affect brain functioning. Many antidepressants treat depression by helping regulate the level of serotonin and other neurotransmitters.
Hormones and Depression
Yet another school of thought suggest hormonal changes can cause depression. Postpartum depression, for instance, describes a depressive episode following birth. A woman’s hormone levels change drastically in the weeks after birth, which is thought to increase the risk of depression. While some new mother’s experience full-blown depression, however, most go through a period of a few days popularly called the “baby blues.” Why some women are more susceptible to postpartum depression than others remains an open question.
Environmental Causes of Depression
Of the four possible causes of depression the role of environmental factors is the hardest to pin down. Life stressors, a loved one’s death, socioeconomic factors—all have been known to trigger depressive episodes. Depression and other illnesses are often seen together. But not everyone experiences depression in response to the same environmental factors, so it’s debatable whether environmental factors are causes of depression or risk factors working in combination with a root cause.
The Complexity of Depression Causes
It’ likely that a single cause for depression doesn’t exist, and that depression is triggered by a complex interaction of genetics, brain chemistry, hormones and environmental factors. Some might say identifying the causes of depression is less importantly than curing depression, but an understanding of the root causes of a depressive episode makes treatment more effective.
Resources
National Institute of Mental Health. (retrieved 31 August, 2009). Depression.
Price, P. (retrieved 3 September, 2009). Genetic causes of depression.
Disclaimer: The information contained within this article is for informational purposes only, and is not intended to be a substitute in any way for care and treatment by a qualified health professional.
Michael McGrath - Michael McGrath began providing web content shortly after finishing his graduate degree in English at the University of Alberta. His broad ...
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