The relationship among stressful life events, our mind and body’s reaction to stress, and the onset of clinical depression is a complex one. Some, but not all, people develop depression after a stressful event in their lives. Either positive or negative events can become a crisis that precedes the development of clinical depression. This is why some patients become more depressed after recovery than they were during the course of care.
In many cases, people become depressed even when there is little or no stress in their lives and everything seems to be going very well. And, no single stressful event will cause depression to develop in every person. The same type of stressor may lead to depression in one person, but not another.
When a stressful experience causes a person to become depressed, it may happen indirectly. A young man with a family history of major depression suffers a serious illness; he may become clinically depressed. It is not necessarily the illness that caused the development of depression, but the combination of a genetic predisposition with the stressful event that made him vulnerable.
For those who struggle with more chronic depression, the effects of stress may be more complicated. A stressful event may trigger the first depressive episode. After that, further depressive episodes may develop spontaneously. Researchers have theorized an explanation called the “kindling effect,” or “kindling-sensitization hypothesis.” This theory holds that past depressive episodes trigger changes in the brain’s chemistry and limbic system that make it more prone to developing future episodes of depression. Early episodes of depression make a person more sensitive to developing depression, even small stressors can lead to later depressive episodes.
Some people may become depressed as a result of having to struggle with chronic stressors. These constant difficulties with pain, financial loss and an empty meaningless existence may be enough to trigger clinical depression.
The theory of “learned helplessness” states that when people experience chronic or repeated stressful events, they learn to feel helpless. This feeling of helplessness is strengthened when a person believes he or she has no control over the stressful situation. Unable to control income, when care is authorized and what a spouse will do in response to changes in the marriage lead the individual to perceive that he/she is helpless to control any aspect of life.