There doesn't appear to be one single cause of depression. Rather, scientists attribute depression to a combination of genetic vulnerability (inheriting certain genes) and environmental factors, with possibly stresses at home, work, or school, involved in the onset of depression.

Genetics: In some families, major depression also seems to occur generation after generation. However, it can also occur in people who have no family history of depression. Whether inherited or not, major depressive disorder is often associated with changes in brain structures or brain function.

Stress and Self Perception: People who have low self-esteem, who consistently view themselves and the world with pessimism or who are readily overwhelmed by stress, are prone to depression. Whether this represents a psychological predisposition or an early form of the illness is not clear.

Physical Changes: Medical illnesses such as stroke, a heart attack, cancer, Parkinson's disease, and hormonal disorders such as an under-active thyroid can cause depressive illness, making the sick person apathetic and unwilling to care for his or her physical needs, thus prolonging the recovery period.

Emotional: a serious loss, difficult relationship, financial problem, or any stressful (unwelcome or even desired) change in life patterns can trigger a depressive episode.

Very often, a combination of genetic, psychological, and environmental factors is involved in the onset of a depressive disorder. Later episodes of illness typically are precipitated by only mild stresses, or none at all.

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Other factors that contribute to depression include:

  • Medications: For some, the symptoms of depression may be the result of long-term use of certain medications, such as some drugs used to control high blood pressure, sleeping pills or, occasionally, birth control pills.
  • Alcohol, Drugs, Tobacco: Using these substances may contribute to depression.
  • Hormones: Women experience depression about twice as much as men, which leads researchers to believe hormonal factors may play a role in the development of depression.

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