What causes depression?

Several factors, or a combination of factors, may contribute to depression.

Genes—people with a family history of depression may be more likely to develop it than those whose families do not have the illness. Older adults who had depression when they were younger are more at risk for developing depression in late life than those who did not have the illness earlier in life.

Brain chemistry—people with depression may have different brain chemistry than those without the illness.

Stress—loss of a loved one, a difficult relationship, or any stressful situation may trigger depression.

For older adults who experience depression for the first time later in life, the depression may be related to changes that occur in the brain and body as a person ages. For example, older adults may suffer from restricted blood flow, a condition called ischemia. Over time, blood vessels may stiffen and prevent blood from flowing normally to the body’s organs, including the brain.

If this happens, an older adult with no family history of depression may develop what is sometimes called “vascular depression.” Those with vascular depression also may be at risk for heart disease, stroke, or other vascular illness.

Depression can also co-occur with other serious medical illnesses such as diabetes, cancer, heart disease, and Parkinson’s disease. Depression can make these conditions worse, and vice versa. Sometimes, medications taken for these illnesses may cause side effects that contribute to depression. A doctor experienced in treating these complicated illnesses can help work out the best treatment strategy.

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