Doctors used to believe that depression was a disease of late life, affecting older people more frequently than younger ones. In fact, recent studies have shown that quite the opposite is true. Depression is slightly more common in people between the ages of 18 and 64 than it is among those over 65.

Even so, depression remains the most common psychiatric disorder among older adults, and it's particularly common among those who are hospitalized for illness or who are living in long-term care facilities. Depression causes untold misery for sufferers and their families alike, and in extreme cases it's so painful and debilitating that people consider and attempt suicide.

The most common type of depressive illness is major depression. Other types of depression that affect older adults include bipolar disorder (also known as "manic depression" ) and dysthymia. Depression can be a special problem in people over age 65 for several reasons:

* While younger people who are depressed tend to have classic symptoms of depression sleep and appetite disturbances, crying, depressed mood older people often develop physical symptoms that may mask the disorder. These include aches and pains, intestinal complaints, breathing problems and feelings of anxiety.

* When asked by a doctor if they feel depressed, older people are more likely to deny feelings of hopelessness and despair.

* Doctors who lack experience with older patients may misdiagnose and mistreat depression, or they may believe it's a normal response to the pressures and losses of old age rather than an illness that can be treated.

* It's often easier for older people who no longer work or care for families to conceal their depression than it is for younger people, who must still show up at the office or take their children to school.

* Because of the stigma associated with depression and other mental illnesses, older people may be reluctant to seek help. They tend to turn their distress in to physical symptoms and then seek medical attention for unexplained headaches, back pain and intestinal problems.

Family History

If a close relative (a grandparent, parent or sibling) has suffered from depression, you are at increased risk. Although this suggests a genetic component to the illness, it's also possible that depression runs in families for other reasons for example, children who are raised by a depressed parent may fail to learn healthy ways of coping with stress, and this can leave them vulnerable to depression. But this doesn't explain why depression is more likely to affect someone whose aunt, uncle or a distant grandparent suffered from it than someone who has no family history of depression.

Early Loss

Researchers have noted a striking pattern of childhood loss among people who suffer from depression for example, the early loss of a parent because of death, divorce or serious illness. This may cause deep-rooted emotional problems that leave them open to depression later in life, especially when they experience other losses.

Physical Illness

Depression often accompanies physical illness, although researchers aren't sure why. It's possible that the stress of illness triggers depression, but in some cases particularly with depression after stroke biochemical changes in the brain may occur that cause depression.

Certain diseases and conditions that seem to trigger depression are more common in older adults for example, cancer, chronic pain, stroke, Alzheimer's and Parkinson's diseases, thyroid failure and vitamin B 12 deficiency. One study found that about half of all people who suffered a heart attack became clinically depressed, and more than 70 percent of them remained that way for at least a year.

Medication

Certain drugs that older people take to treat other illnesses are known to cause mood changes as a side effect. If you think your depressed mood may be related to a medication, tell your doctor. She may decide to switch you to a different class of drug.