Depression and Alzheimer's Linked
Depression Boosts Risk of Dementia, but Does Not Increase During Early Alzheimer's, Studies Show
Depression and Alzheimer's: Role of History Study continued...
Depression at the start of the study was not associated with an increased risk for Alzheimer's disease.
The researchers then looked at who had depression and who did not, and compared the sizes of their hippocampus and amygdala. They found no association between the sizes of those brain areas and depression, refuting the idea that the shrinkage in the brain contributes to the Alzheimer's disease.
"Our findings definitely do not support the notion that depression leads to loss of hippocampus and amygdala cells which then leads to Alzheimer's," says Monique M.B. Breteler, MD, PhD, professor of neuroepidemiology at Erasmus University and the study's lead author, in an email interview.
Yet a third factor, she says, could be causing both depression and Alzheimer's, and more research is needed to find out exactly what.
The study is published in Neurology.
Depression and Alzheimer's Early Stages Study
In the second study, researchers from Rush University Medical Center, Chicago, looked at participants' state of mind during the very early stages of Alzheimer's disease and whether they tended to become more depressed.
Some experts have suggested depression is not a true risk factor but a consequence of the disease. If that is true, depression would likely increase as a person develops dementia.
For up to 13 years, researchers followed 917 participants of the Religious Orders Study, which launched in 1994 and includes Catholic nuns, priests, and monks. All were free of dementia at the study start and all agreed to donate their brains for autopsy at death so researchers can discover more information about Alzheimer's disease and other problems.
They were given annual exams, including tests of memory and other cognitive skills. During the follow-up, 190 developed Alzheimer's disease. Those with more depression at the beginning were found more likely to get it. But their depression didn't increase in the early stages.
"We found absolutely no evidence that depressive symptoms increased during that period [of early Alzheimer's],'" says Robert S. Wilson, PhD, professor of neurological sciences and behavioral sciences at Rush University Medical Center, Chicago, and the lead author.
"Even though it sort of makes sense that you would get depressed when you are losing cognition, it doesn't seem to be happening."
The research, he tells WebMD, "goes against the idea that depressive symptoms are a consequence not a risk factor of Alzheimer's disease."
The study is published in the Archives of General Psychiatry.