According to a study published in the April 8, 2008, issue of Neurology®, the medical journal of the American Academy of Neurology, people who have had depression are more likely to develop Alzheimer’s disease (AD) than people who have never had depression.
It has been theorized that depression my increase the risk for Alzheimer's disease, but it has been unclear if the risk is impacted by structural brain changes. One theory was that depression leads to loss of cells (atrophy) in two areas of the brain, the hippocampus and the amygdala, which then contributes to Alzheimer’s disease.
- The study included 503 participants between the ages of 60 and 90 who had no dementia.
- Participants reported their history of any depressive episodes.
- Depressive symptoms were assessed utilizing the Center for Epidemiologic Studies Depression Scale.
- Assessment of the hippocampus and amygdala was performed via three-dimensional MRI.
- Participants were followed for an average of six years, observing for development of AD.
- One hundred thirty-four of the study participants (26.6%) reported a history of depression.
- Eighty-eight of the 134 reported onset before the age of 60. (Reporting at least one episode of depression that prompted them to seek medical advice.)
- Forty-six of the 134 reported late onset depression.
- Three-dimensional MRI analysis did not reveal any significant association with hippocalmpal or amygdalar volume (size).
- Thirty-three study participants developed AD during the study follow-up period.
- Analysis revealed that participants with early onset depression had an increased risk for AD, independent of hippocampal or amygdalar volume.
- Depressive symptoms at the beginning of the study were not associated with increased risk of AD.
Study author Dr. Monique M.B. Breteler, with the Erasmus University Medical Center in the Netherlands, commented,
“We don’t know yet whether depression contributes to the development of Alzheimer’s disease or whether another unknown factor causes both depression and dementia... We’ll need to do more studies to understand the relationship between depression and dementia.”