Recent research has shown consistently that depression rarely is due to a single event or condition. Rather, the development of depression is a complicated cognitive, behavioral, hormonal and biochemical process.
A person’s genetic factors may create a predisposition for or vulnerability to depression. It is clear that depression, like many other illnesses, tends to run in families. For example, a child with one parent with depression has a 10 to 13 percent greater chance of developing depression. Whether this vulnerability results in depression may depend on the person’s life stress, early family life, coping strategies and social support.
A chemical imbalance of biological factors including hormones and other substances naturally found in the body—including estrogen, serotonin, cortisol and melatonin—plays a role in triggering many forms of depression. For example:
- Changing levels of estrogen during a woman’s life are linked to several forms of depression unique to women.
- Serotonin is a brain chemical that carries messages between brain cells.
- The rate of serotonin synthesis is 52 percent higher in men than in women, and researchers are investigating if this helps explain why depression is two to three times more common in women.
- Women and men typically produce different levels of melatonin, a chemical involved in regulating many body functions in relation to natural light (example: tanning of skin) and investigators are looking at whether this plays a role in Seasonal Affective Disorder which affects women three times more often than men.
Researchers are trying to understand better how these and other biological factors provoke depressive episodes so that, in the future, depression can be prevented, better treated or cured.
The reaction to stress in our lives has unseen negative impacts on our bodies and contributes to the development of a wide range of diseases including heart disease, the common cold and depression. Stress or the reaction to it may contribute to chemical imbalances associated with depression. Perhaps people with a family history of depression have inherited a greater susceptibility to develop depression because of the way their bodies have been genetically programmed to react to stressful events.
Depression has been reported since the beginning of civilization and each generation has sought to understand what causes the debilitating condition. Hippocrates, the father of medicine, in 4 B.C. thought that depression was due to excessive black bile in the spleen. The ancient Egyptians believed that this black bile was due to the influence of the planet Saturn (a “saturnine” mood is a dark, unhappy one). Throughout history depression has been blamed on melancholic temperament (example: Aristotle), demons, damaged paternal sperm (example: Ishaq Ibn Imran) and anger turned inward (example: Freud).
While our understanding of causes for depression has changed and will continue to progress, the disease has affected young and old, rich and poor, famous and common throughout history.
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Michael Herkov, Ph.D., and Wayne Goodman, M.D. also contributed to this article.