How do mood and anxiety disorders increase the risks of dementia?
It is not clear why mood and anxiety disorders predict dementia. One strong possibility is that an underlying biological mechanism connects the disorders. Depression, for some people, may be an early sign of dementia.
Anxiety may be the result of cognitive impairments that are very mild at first. That is to say, the subtle biological changes that result in the depressive or anxiety disorders, eventually disrupt the function of the brain and result in dementia.
For most of the dementias, the vast majority of which are Alzheimer Dementia, symptoms appear many years after the biological processes have begun. It is possible that the disorders are related by chance, i.e., that the genes responsible for the disorders happen to sit relatively close to each other on chromosomes.
Thus people who have depression or anxiety, which will show up earlier in life than does dementia, are also likely to get dementia.