The associations were particularly strong for cardiovascular disease. Those in the quarter with the highest optimism scores had a nearly 40 percent lower risk for heart disease and stroke than those in the lowest quarter, even after controlling for other health factors. The associations with cancer were also significant, but weaker.
“People can have low optimism for a wide array of reasons,” said the lead author, Eric S. Kim, a research fellow at the Harvard T.H. Chan School of Public Health. “Twin studies show it’s about 25 percent heritable, but that means it’s 75 percent social circumstances or under our own control.”