Working more than 25 hours a week makes people dumber
Researchers wanted to test the whole "use it or lose it" theory about working adults -- the conventional wisdom says that continuing to hold down a job helps people stay sharp as they get older, an argument often used to defend raising the retirement age.
The results suggest that the hypothesis is true... up to a point. Specifically, up to 25 hours per week, and cognitive function really went downhill when subjects worked 40 or more hours a week. So the steadfast American belief that working longer hours is better for success, mental function, and overall quality of life is totally BS.
In fact, the standard workweek could be making people dumber. Adults in the US work an average of 47 hours a week, which means we're overworking ourselves into a nation of idiots.