Peto believes that the previously established connections between unhappiness and earlier death were actually “reverse causality,” in which unhappiness was a byproduct of the illnesses that led to death.
“In our view, the previous studies haven’t been well done,” he says. “All that’s going on is ill health actually was causing unhappiness and stress. There’s a pathetic old joke, where the question is ‘What's the most dangerous place in the world to be?’ and the answer is ‘Bed, look at the number of people who die in bed.’ Well, that's just a pathetic old joke, but that’s reverse causality.”
In an initial analysis, the Lancet study did find an association between mortality and unhappiness, but that association disappeared once they adjusted for baseline health.
“I think the interesting implication is we’ve got very few things that really matter as far as health is concerned,” Peto says. He names smoking and obesity as two things that are very good predictors of mortality. But unhappiness, it seems, is not at all on their level.
“You could say it’s good news for the grumpy,” he says.
