Cognition not directly affected by depression

There appears to be no association between depressive symptoms and subsequent cognitive decline in older adults, according to the findings of a study conducted by researchers in Pennsylvania.

Over a 12-year period, Dr. Mary Ganguli of the University of Pittsburgh School of Medical and colleagues examined the association between depressive symptoms and subsequent cognitive decline in 1265 nondemented adults 67 years of age or older.

At follow-up, 1094 subjects were still dementia free and 171 had developed dementia.

In the dementia-free subjects, those with depressive symptoms at baseline had significantly lower baseline scores on all cognitive measures than nondepressed patients. Among those who eventually developed dementia, depression was associated with worse performance on some but not all cognitive measures.

The dementia-free group experienced minimal cognitive decline over time, whereas marked decline occurred in subjects who later developed dementia, the team reports in the Archives of General Psychiatry. No association was observed between depressive symptoms and the rate of cognitive decline over time in either group.

"If an older person is depressed and performs poorly on cognitive tests, the two may well be related," Ganguli said in an interview. "However, if the person continues to decline cognitively over time, that decline is likely not due to depression; it is more likely due to an incipient dementia which will manifest itself down the line."

"Once we separate out the effect of an underlying dementia, depression does not seem to lead to further cognitive decline," she notes.

SOURCE: Archives of General Psychiatry, February 2006.