While there appears to be some connection between depression in late life (and possibly earlier in life) and dementia, as I mentioned on Tuesday, many questions remain.
An editorial by Dr. Alex Mitchell of Leicester, U.K. also advises caution in jumping to conclusions. There are study flaws to be sorted out. Also, at least one proposed mechanism for such a relationship (microvascular changes) doesn’t quite add up. And, as I mentioned before, there is no clear cause-and-effect “smoking gun”.
Studies done by Dr. Sonia Lupien in Montreal suggest a strong association between chronic stress and cognitive decline, so there may be overlap here.
Bottom line: there’s still a lot to sort out. Here is the full editorial by Dr. Mitchell: http://ageing.oxfordjournals.org/cgi/reprint/34/3/207.pdf
and a post I wrote two years ago on Dr. Lupien’s research: http://changingaging.org/2008/10/02/power-up-stress-brain-drain/