NEW YORK, Nov 05 (Reuters Health) -- Studies have suggested that brain changes resulting from disease may be the underlying cause of many cases of depression in the elderly. But a new report suggests that the physical effects of disease, such as stroke, are more likely to be the cause of depression in geriatric patients than brain lesions seen on imaging studies of the brain.
"It's always difficult to sort out which comes first, the physical and cognitive (learning and memory) limitations or a brain lesion on MRI," said Dr. Linda P. Fried from Johns Hopkins University School of Hygiene and Public Health in Baltimore, Maryland, in an interview with Reuters Health. Her group's findings are published in the November 1st issue of the American Journal of Epidemiology.
The investigators examined the relationships between magnetic resonance imaging (MRI)-detected abnormalities, physical and mental function, and symptoms of depression among 3,658 men and women who participated in the Cardiovascular Health Study.
Contrary to previous reports, the authors write, abnormalities within one particular area of the brain -- the basal ganglia -- were not associated with depressive symptoms, while abnormalities outside that area did appear to be associated with depression.
Even more important than brain abnormalities, though, were limitations in activities of daily living (ADL), including basic functions such as the ability to wash, dress, and feed oneself, and the ability to move around, the results indicate. "Difficulty in performing one or more instrumental ADL tasks was the variable most strongly associated with depression levels," the investigators report. Instrumental ADL tasks include such activities as using the telephone, shopping, preparing meals, and managing finances.
According to the report, age was not related to depression levels, but being female was. Women were more likely than men to develop symptoms of depression.
"The results from this study are quite contrary to what the literature has suggested is a direct and causal relation between basal ganglia (abnormalities) and depression," the researchers observe. This study "did not find an independent association between basal ganglia (abnormalities) or any other MRI (changes) and depressive symptoms after adjustment for physical and cognitive function."
Still, the investigators note, distinguishing between brain abnormalities and functional limitations as causes of depression is often impossible. What these findings mean, though, is that doctors should look for both ADL limitations and MRI changes when they are trying to sort out the cause of depression in a given patient, said Fried.
