Last year, Medical News Today reported on a studyby researchers from the University of Amsterdam, suggesting elderly depression may increase the risk of dementia and mild cognitive impairment. Other studies have supported this claim, but the mechanisms underlying this association have been unclear. Now, a new study published in the journal Neurology sheds some light on how depression and dementia are related. Study author Robert S. Wilson, of Rush University Medical Center in Chicago, IL, notes that the suggested relationship between depression and dementia has raised many questions. 

"Is the depression a consequence of the dementia?" he asks. "Do both problems develp from the same underlying problems in the brain Or does the relationship of depression withdementia have nothing todo with dementia-related pathology?" In an attempt to answer these questions, Wilson and colleagues analyzed 1,764 people of an averageage of 77, who were a part of the Religious Orders Study and the Rush Memory and Aging Project. 

All participants were free of any memory orthinking problems atstudy baseline. Each year for an average of 7.8 years, subjects were assessed for symptoms of depression, such as reduced appetite and loneliness, and took part in tests that gauged their memory and thinking skills. 

Link between depression and dementia 'independent of dementia-related brain changes' During the study period, 680 people died. Autopsies were performed on 582 of these individuals to identify any brain plaques or tangles related to dementia, as well as any other indications of brain damage. 

The researchers found that 315 (18%) participants developed dementia during the study period, while 922 (52%) participants developed mild cognitive impairment (MCI)) a condition that is a common precursor toAlzheimer's disease, the most common form of dementia. 

According to the researchers, no relationship was found between the levels brain damage among participants and the levels of depressive symptoms or changes in depressives symptoms. This indicates that the relationship between depression and dementia is independent of the brain changes caused by dementia, theteam says. 

The investigators found that those who developed MCI were more likely to have a higher level of depressive symptoms prior to MCI diagnosis. However, compared with those who did not develop MCI, they were no more likely to experience any change in symptoms of depression following MCI diagnosis. 

Participants who developed. dementia were also more likely to have a higher level of depressive symptoms before dementia diagnosis, according to the researchers. But after diagnosis, their depressive symptoms were more likely to reduce rapidly. 

Overall, having a higher level of depressive symptoms was linked to faster cognitive decline, according to the researchers. 

They note that depressive symptoms accounted for 4-4% of the variability in cognitive decline that could not be attributed to levels of brain damage. Commenting on the study results, Wilson says: 

"These findings are exciting because they suggest depression truly is a risk factor for dementia, and if we can target and prevent or treat depression and causes of stress".