New study links psychological well being with dementia

I guess it's not a direct cause but more like if you are unhappy you will be less active mentally and physically.

Having read the article the research appears inconclusive, l think OPs title should read
"New study MAY link psychological well being with dementia - maybe, maybe not, moreso if you are white and female"

Recently there have been a number of articles telling us what increases our risk of developing dementia - but they are usually things that we can't do anything about. Nobody chooses to have poor psychological wellbeing - and if they aren't happy the last thing they need is to be told they are likely to get dementia!
Lack of sleep has also been flagged as increasing the risk. Which seems to imply the people who sleep badly are doing so deliberately!
I'm all in favour of being informed if the advice is achievable. The rest of it feels like pointless scaremongering