Depression and Alzheimer's Linked
Depression Boosts Risk of Dementia, but Does Not Increase During Early Alzheimer's, Studies Show
April 7, 2008 -- A history of depression, especially if it occurs early in life, boosts
your risk of getting
Alzheimer's disease, according to a new study.
But depression does not seem to increase during the early stages of
Alzheimer's disease, according to another new study, refuting the idea that the
Alzheimer's causes the depression, as some claim.
Together, the two studies contribute some answers to the ongoing debate
about depression and Alzheimer's disease -- and whether depression triggers the
Alzheimer's disease, the Alzheimer's disease triggers the depression, or yet
another risk factor leads to both. Up to 50% of Alzheimer's patients also
The new research strengthens advice to take depression seriously and get
treatment, says Gary Kennedy, MD, director of geriatric psychiatry at
Montefiore Medical Center, New York, N.Y. "You want to get over it as
quickly and completely as possible," says Kennedy, who reviewed the studies
Depression and Alzheimer's: Role of History Study
To look at the link between depression and Alzheimer's disease, researchers
from Erasmus Medical Center in the Netherlands assessed 503 men and women, aged
60 to 90 at the study start and free of dementia. All were participants in the Rotterdam Scan
Study, an ongoing research effort to look at chronic diseases in the
Participants reported any history of depression and noted if it occurred
before or after age 60. They also reported any symptoms
of depression at the study start.
Researchers also performed three-dimensional
MRI scans to look at the volume of two brain areas -- the hippocampus and
the amygdala, two areas that some experts say shrink in those with depression.
They wanted to see if they could document that suspected association.
After a six-year follow-up, 33 people developed dementia; 134 of the
participants had a history of depression (88 early onset, 46 late).
If the depression occurred before age 60, the researchers report, the risk
of getting Alzheimer's disease later was nearly four times as great as for
those who did not have a history of depression. If the depression occurred
after age 60, the risk was about 2.5 times greater than the risk for the
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.