Depression comes in many forms. Mild depression may range from the colloquial use of “I’m having a bad day” to depressive symptoms that are not severe or pervasive enough to meet current diagnostic standards for Major Depressive Disorder (which is more severe and has to persist for at least two weeks). Dysthymia is an enduring but comparatively mild form of depression. Sadly, recent surveys indicate that as many as 40% of community dwelling elders (by most standards those over 55) have some form of depression. This puts those afflicted at greater risk of mortality and suicide as well as poorer quality of life than those who are not depressed.

Does having a diagnosis of dementia increase the prevalence of depression in the elderly? The answer depends on the cause of dementia. The prevalence of depression in dementia due to Alzheimer’s disease is estimated to be between 20-40%. This is true for all stages of Alzheimer’s disease and is slightly lower than for community dwelling elders who are not demented. Depression is more likely to occur with dementias due to either vascular disease (strokes) or Lewy body disease than with Alzheimer’s disease.

What are the mechanisms associated with depression when it occurs in Alzheimer’s disease? One possibility is that genetics determines who will become depressed and who won’t. But genetics explains only about 8% of the variance in studies of Alzheimer’s disease. Furthermore, there is no association between the putative pathology of Alzheimer’s disease (i.e., plaques and tangles at autopsy or amyloids in cerebrospinal fluid) with depression. Interestingly, there is also no association between cerebrovascular disease in those with Alzheimer’s disease and depression.

Does being diagnosed with dementia lead to an increase in depression? Apparently not. A recent prospective study indicated that there was little change in mood during the first 2-3 years after being diagnosed with dementia. Therefore, there is no catastrophic reaction to a diagnosis of dementia. On average, those who were depressed to start stayed depressed and those were not depressed do not become depressed.

Does placement in skilled nursing home of those with moderate to severe dementia make them depressed? Not as much as one would intuitively expect. The prevalence of depression after placement is about 21% (the incidence is about 15%). But if placement induces depression, the depression persists in about 45% of cases. Therefore, depression is not an inevitable outcome of placement (stressful adjustments do not always lead to depression).

Does being depressed make dementia more likely in the elderly? There are several studies indicating that being depressed and over 55 doubles the risk for dementia in the elderly. The largest study involved 280,000 veterans over 55 and concluded that there was two times the risk of dementia in veterans who were depressed when compared to those who weren’t. So depression increased the risk of dementia but dementia does not appear to increase the risk of depression.

In conclusion, contrary to intuitions, being demented does not necessarily cause one to be depressed. Furthermore, being diagnosed with dementia or being placed in a care facility does not necessarily lead to depression. Depression is common but not inevitable outcome for all of us as we age. Next week, what are the treatments for depression? How well do different treatments work for those who are demented as well as for those who are not?