Once again we're hearing there's a correlation between depression and dementia in older adults, but now we have more details about how they affect each other.
Last year, The British Journal of Psychiatry compared more than 20 different studies that researched the link but was unable to say which caused the other.
But Wednesday the journal Neurology released the findings of a study suggesting it's depression that contributes to dementia.
This study included more than 1,700 older adults who had no signs of dementia at the beginning of the study. In the end, researchers discovered those who had depression were more likely to develop the disease later on. As for why — that question remains.
Time notes, "Some research suggests that people with depression may have high levels of hormones that interfere with the region of the brain responsible for learning and memory aptitude."
But again — that's just a theory. Another is inflammation of the nervous systems of those with depression. The thinking there is that somehow that inflammation makes blood flow to the brain difficult.
Either way, a professor of psychiatry told The New York Times, "We think depression is toxic to the brain, and if you're walking around with some mild brain damage, it will add to the degenerative process."
HealthDay pointed out this means treating depression early could help prevent dementia later on.
Researchers are now looking at exactly how depression increases the risk of dementia so that better treatment may be provided.
