So we are finally coming around to discovering at the molecular level what has been known since forever: that on average positive, non-stressed out people tend to be healthier and live longer than those depressed or otherwise psychologically afflicted. And honestly when the brain has a critical influence on almost all major organs so I don't see why scientists are excited to find that it might have an effect on the ageing process too. The molecular mechanism may be exciting, but the fact itself is entirely expected.
There's a difference between suspecting something and knowing it.
E.g. a lot of country sayings might offer an interesting starting point to figure out if there's some truth to them and some interesting things to discover there but by no means they are proof of anything.
While I don’t mean to speak negatively of peer reviewed journals, I don’t think “the scientific method” and “getting published in a highly regarded peer reviewed journal” are synonymous.
If there were no journals, I don’t think they would have to be created before anything counted as being done using the scientific method.
Though, I do agree that peer review is very useful.
I don't care about stress. I personally want to stimulate my brain to the maximum as much as I can. I don't know whether this would lower my life span.
You might want to rethink your assumptions here. Stress generally makes you less productive. And there are plenty of long-lived people of high accomplishment.