Although individuals with depression may be more likely to develop Alzheimer's disease, symptoms of depression do not appear to increase in the years before a diagnosis is made, according to a report in the April issue of Archives of General Psychiatry, one of the JAMA/Archives journals.
This suggests that depression is not a consequence of developing Alzheimer's disease but may instead be a risk factor for dementia.
Previous studies have found higher levels of depressive symptoms (such as feeling sad) among patients with Alzheimer's disease and its precursor, mild cognitive impairment, according to background information in the article. “The basis of this association is uncertain, however,” the authors write. “A leading hypothesis is that depressive symptoms do not constitute a true risk factor but rather a consequence of the disease.” If this were the case, symptoms of depression would likely increase during the early stages of Alzheimer's disease.
Robert S. Wilson, Ph.D., of Rush University Medical Center, Chicago, and colleagues studied 917 older Catholic nuns, priests and monks who did not have dementia beginning in 1994. Participants had a yearly clinical evaluation that included a neurological examination, cognitive (thinking, learning and memory) testing and classification of Alzheimer's disease or mild cognitive impairment. They also completed a 10-item scale assessing their symptoms of depression.