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Depression has been part of the human condition since antiquity. Hippocrates is generally credited with the first description of an affective disorder and is thought to have coined the term "melancholia," literally translated as "black bile."(1)
Although life is filled with unexpected events such as the death of a loved one, loss of a job, major illness, or other catastrophic events, not everybody becomes depressed. Most individuals suffer only transient, dysphoric feelings and find ways to adjust to life's challenges. However, there are certain individuals who, when faced with such psychosocial stressors, experience a major depressive episode.
Depression has been classified as a mood disorder or affective disorder. Mood is defined as a pervasive and sustained emotion that, in the extreme, markedly affects a person's perception of the world and ability to adequately function in society.(2) Mood disorders are among the most common encountered in clinical practice and are divided into depressive disorders and bipolar disorders.
Depression is a common disorder that affects approximately 5 percent of the population at any given time, and about 30 percent of adults will suffer from depression over a lifetime. (3) Commonly thought of as a disorder of young to middle adulthood, with an average age of onset in the late 20's, depression is also recognized as a common psychiatric illness in the elderly.(4) Women are two to three times more likely to suffer from depression than men.(5) Rates of depression increase with the presence of concomitant medical illnesses, including myocardial infarction survivors (40-65 percent), diabetic patients (8.4–32.4 percent), cancer patients (25 percent), and stroke survivors (10-27 percent).(6)
There are over 187 million adults in the United States – and about 19 million of these people will experience a depressive episode in any given year, making depression the most common psychiatric disorder encountered in general medical practice. (7) In 1990, depressive disorders cost the U.S. economy approximately 44 billion dollars, and of this, almost $12.4 billion was spent on diagnosis and treatment.(8)
Mood disorders, depression, and anxiety are common illnesses in our society. Lost work time, family conflicts, personal strife, and other consequences of the disease can eventually lead to complete disruption of one's life. Depression and mood disorders have become increasingly recognized as common, yet under-diagnosed and under-treated conditions.(9)
The etiology of depressive disorders is too complex to be totally explained by a single social, biologic, or developmental theory. Several factors seem to work together to cause or precipitate depressive disorders. Heredity does seem to have a role, as studies have shown. Depressive disorders and suicide tend to cluster in families, and first-degree relatives of patients with depression are one and one half to three times more likely to develop depression than normal controls.(10) The symptoms reported by patients with major depression consistently reflect changes in the brain monoamine neurotransmitters, specifically norepinephrine, serotonin, and dopamine.(11)
Depleted serotonin due to prolonged stress, adrenal exhaustion, hypothyroidism, heavy metal toxicity, and "leaky gut" syndrome with subsequent food intolerance, and deficiencies in B12, folic acid, and amino acids, are some of the secondary factors contributing to depressive states.
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