Causes and Risk Factors
Several lines of research have shown that depressive illnesses are disorders of the brain. But the exact causes for these illnesses are not yet clear and are still being studied.
Changes in the Brain
Imaging technologies such as magnetic resonance imaging (MRI) scans show that the brains of people with depression look different than those of people without the illness. The scans show that the areas of the brain that control moods, thinking, sleep, appetite, and behavior are not functioning properly. The scans also reveal imbalances in important brain chemicals called neurotransmitters that allow brain cells to communicate with each other. But these images do not yet reveal WHY the depression has occurred.
Many Possible Causes
In general, there is no one cause or risk factor for depression. It most likely results from many factors, such as family history, life experiences, and environment. Older adults with depression may have had it when they were younger, or they may have a family history of the illness. They may also be going through difficult life events, such as losing a loved one, a difficult relationship with a family member or friend, or financial troubles.
For older adults who experience depression for the first time later in life, other factors may be at play. 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 harden 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 some doctors call "vascular depression." Those with vascular depression also may be at risk for other vascular illnesses, such as heart disease, or stroke.
Depression Can Occur With Other Illnesses
Depression can also co-occur with other serious medical illnesses such as diabetes, cancer, 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.
Because many older adults face these illnesses along with various social and economic difficulties, some health care professionals may wrongly conclude that these problems are the cause of the depression -- an opinion often shared by patients themselves.
All these factors can cause depression to go undiagnosed or untreated in older people. Yet, treating the depression will help an older adult better manage other conditions he or she may have.