There has been much activity, questions and concerns about depression..
The Neurology Now magazine can be located on-line for those who would like to subscribe. The magazine is by the American Academy of Neurology and the American BRAIN Foundation.
I just received my April/May 2015 magazine which has one article "Can Depression Signal Dementia?" ..."for which studies have not been completed".
Scanning it briefly, towards the end, "Dementia-Depression Link"...that does state "Research has not proved that people with depression are more likely to develop dementia."
But, because we do not know, for ourselves, or others in the future, it can/may be a subject of interest. And, overall, it is a good magazine on neurology.