Depression is unusually common among people with Alzheimer’s disease. In the general population, about 6 percent of men and women over 65 have a bout of the blues each year. By contrast, 40 to 50 percent of people with Alzheimer’s experience some symptoms of depression. And 10 to 20 percent develop a longer-lasting, more severe form of the mood disorder, known as major, or clinical, depression.
Moreover, depression rates are elevated among people who have other types of dementia, as well as among individuals with mild cognitive impairment (MCI), a condition that often precedes Alzheimer’s.
In their search for a better understanding of the links between depression and these conditions, investigators have uncovered two surprising findings:
- People with dementia often fail to display the classic symptoms of depression.
- Treatment with the most commonly prescribed type of antidepressant may not be effective.
Just about everyone feels down in the dumps now and then, but major depression is a medical condition that can have profound consequences. People who have it live for prolonged periods with feelings of sadness, anger and hopelessness. They often lack energy and may lose their appetites and interest in favorite activities.
Depression can cause poor concentration and sleep problems, and lead people to become socially withdrawn, or obsessed with thoughts of death or harming themselves. People with Alzheimer’s can exhibit these classic signs of depression, and if they occur in the early stages of cognitive decline before a diagnosis has been made, it can be difficult to distinguish between the disorders.
Doctors have also observed that some people with Alzheimer’s and other forms of dementia experience symptoms not normally associated with depression. Perhaps the first clear portrait of this situation comes from a 2003 study in The American Journal of Psychiatry. Researchers assessed 394 elderly people to determine if they suffered from depression; 243 were presumed to have Alzheimer’s and 151 were cognitively healthy. Nearly 50 percent of people with Alzheimer’s had experienced at least one episode of major depression during their lifetimes, as had 28 percent of their cognitively healthy counterparts.
However, a comparison of the participants’ most recent episode of major depression revealed that the mood disorder took on a decidedly different appearance, or character, in individuals with Alzheimer’s.
While difficulty concentrating is one of the symptoms commonly associated with depression, Alzheimer’s patients were significantly more likely than those without it to report that they had experienced this problem. In addition, they were significantly more likely to say that they had been indecisive.
Also noteworthy, people with Alzheimer’s were significantly less likely to report having experienced sleep problems or feelings of worthlessness and excessive guilt while depressed-all common features of major depression in general and among the cognitively intact seniors in the study.
And unlike their counterparts who didn’t have Alzheimer’s, some Alzheimer’s patients experienced hallucinations and delusions during periods of depression. More recently, others have observed that depression in a person with dementia is more likely to bring on other psychological problems, such as apathy and irritability. Other studies have found that some people with depression who do not develop dementia don’t have hallucinations and delusions.