There appears to be a complex relationship among stressful situations, our mind and body’s reaction to stress, and the onset of clinical depression. It is clear that some people develop depression after a stressful event in their lives.

Events such as the death of a loved one, the loss of a job, or the end of a relationship are often negative and traumatic and cause great stress for many people. Stress can also occur as the result of a more positive event such as getting married, moving to a new city, or starting a new job. It is not uncommon for either positive or negative events to become a crisis that precedes the development of clinical depression.

Whether a stressful event itself can actually cause a person to become depressed is not fully known. There are times when we all must struggle with very painful situations in our lives. More times than not these changes do not result in a person becoming clinically depressed. In fact, sometimes 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.

If a stressful experience causes a person to become depressed, it may happen indirectly. In other words, if a young woman with a family history of major depression suffers the death of a loved one, she may become clinically depressed. In this situation it is not necessarily the traumatic loss itself that caused the development of depression, but the combination of a genetic predisposition with the stressful event that made her vulnerable to becoming depressed.

For those who struggle with more chronic depression, the effects of stress may be more complicated. A stressful event such as a job loss or the death of a loved one is more likely to come before a first or second depressive episode. After that, further depressive episodes may develop spontaneously. It is not certain why stress may lead to depression in this way. However, researchers have theorized an explanation called the “kindling effect,” or “kindling-sensitization hypothesis.” This theory surmises that initial depressive episodes spark changes in the brain’s chemistry and limbic system that make it more prone to developing future episodes of depression. This may be compared to the use of kindling wood to spark the flames of a campfire. Since 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 stress. These constant difficulties may come in the form of having to juggle multiple roles at home and work, making major changes in lifestyle, being in an abusive environment, etc. They may also come with important and normal transitions in life such as late adolescence and early adulthood when many people separate from their families to establish their own independence. Middle age may require adjustment to changes in fertility and virility, children leaving the home, concern about job advancement, and a re-evaluation of accomplishments in life. Retirement is another time of major change as some people struggle with a reduction of position and finances. If a person is under continuous stress, a single difficult event may be more likely to induce a depressive episode. For instance, if a middle-aged woman is in an unhappy marriage, she may be more likely to become depressed after her youngest child leaves home for college. The event of her child leaving home may not by itself have been enough to lead to depression, but the constant stress of an unhappy marriage combined with this event may be enough to trigger clinical depression.

In studying how stressful events may lead to depression, researchers have developed a theory called, “learned helplessness.” This theory 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. Although the research to support this theory was initially done with animals, the effects of learned helplessness may be seen in depressed humans. People who are depressed very often have negative beliefs about their ability to manage aspects of their lives based on perceived failures in the past. For example, imagine an adolescent girl living in a home with verbally abusive parents who tell her that she is stupid and cannot do anything right. Over time the young girl may believe her parents and come to doubt her abilities and self-worth. She may begin to feel helpless and believe that most things are beyond her control. This feeling of helplessness may make her vulnerable to developing clinical depression at some point in her life.