It's not known exactly what causes depression. As with many mental disorders, a variety of factors may be involved, such as:

  • Biological differences. People with depression appear to have physical changes in their brains. The significance of these changes is still uncertain, but may eventually help pinpoint causes.
  • Brain chemistry. Neurotransmitters are naturally occurring brain chemicals that likely play a role in depression. When these chemicals are out of balance, it may be associated with depressive symptoms.
  • Hormones. Changes in the body's balance of hormones may be involved in causing or triggering depression. Hormone changes can result from thyroid problems, menopause or a number of other conditions.
  • Inherited traits. Depression is more common in people whose biological (blood) relatives also have this condition. Researchers are trying to find genes that may be involved in causing depression.
  • Life events. Traumatic events such as the death or loss of a loved one, financial problems, high stress, or childhood trauma can trigger depression in some people.
Feb. 21, 2014