Causes

It's not known exactly what causes depression, but a variety of issues may be involved. These include:

• Brain chemistry. Neurotransmitters are naturally occurring brain chemicals that carry signals to other parts of your brain and body. When these chemicals are abnormal or impaired, the function of nerve receptors and nerve systems changes, leading to depression.
• Hormones. Changes in the body's balance of hormones may be involved in causing or triggering depression.
• Inherited traits. Depression is more common in people whose blood relatives — such as a parent or grandparent — also have the condition.
• Early childhood trauma. Traumatic events during childhood, such as physical or emotional abuse, or loss of a parent, may cause changes in the brain that make a person more susceptible to depression.
• Learned patterns of negative thinking. Teen depression may be linked to learning to feel helpless — rather than learning to feel capable of finding solutions for life's challenges.