More than 60 years ago, the World Health Organization defined health as a “state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.” Just because you’re not depressed doesn’t necessarily mean you’re happy. But, if you look in the medical literature, there are 20 times more studies published on health and depression than there are on health and happiness. In recent years, though, research on positive psychology has emerged, and we’re now asking what we can do to increase our success, functioning, and happiness. Although these are all inherently good in themselves, what about the question I address in my video Are Happier People Actually Healthier?

“There is growing evidence that positive psychological well-being is associated with reduced risk of physical illness,” but it’s not surprising that healthier people are happier than sick people. “The intriguing issue is whether psychological well-being protects against future illness or inhibits the progression of chronic disease.” To figure out which came first, you’d have to get more than just a snapshot in time. You would need prospective studies, meaning studies that go forward over time, to see if people who start out happier do, in fact, live longer. A review of such studies indeed “suggests that positive psychological well-being has a favorable effect on survival in both healthy and diseased populations.”

Not so fast.

Yes, positive states may be associated with less stress, less inflammation, and more resilience to infection. But, positive well-being may also be accompanied by a healthy lifestyle that itself reduces the risk of disease. Happy people tend to smoke less, exercise more, drink less alcohol, and sleep better. So, maybe happiness leads to health only indirectly. The apparent protective effect of positive psychological well-being, however, persists even after controlling for all these healthy behaviors. This means that even at the same level of smoking, drinking, exercising, and sleeping, happier people still seem to live longer.

Ideally, to establish cause-and-effect definitively, we’d do an interventional trial, in which participants would be assigned at random to different mood levels and tracked for health outcomes. It’s rarely feasible or ethical to randomly make some people’s lives miserable to see what happens, but if you pay people enough you can do experiments like the one whose objective stated: “It has been hypothesized that people who typically report experiencing negative emotions are at greater risk for disease and those who typically report positive emotions are at less risk.” Researchers tested this using the common cold virus. Three hundred and thirty-four healthy volunteers were assessed for how happy, pleased, and relaxed they were, or how anxious, hostile, and depressed. Subsequently, they were given nasal drops containing cold rhinoviruses to see who would be more likely to come down with the cold. Who would let someone drip viruses into their nose? Someone paid $800, that’s who!

Now, just because you get exposed to a virus doesn’t mean you automatically get sick. We have an immune system that can fight it off, even if the virus is dripped right into our nose. But, whose immune system fights better?

In one-third of the bummed out folks, their immune systems failed to fight off the virus and they came down with a cold. But only about one in five got a cold in the happy group. Could it be that those with positive emotions slept better, got more exercise, or had lower stress? No. It appears that even after controlling for the healthy practices and levels of stress hormones, happier people still appear to have healthier immune systems and a greater resistance to developing the common cold.

It also works with the flu. When researchers repeated the study with the flu virus, increased positive emotions were associated with decreased verified illness rates, just like in their earlier study on colds. These results indicate that feeling vigorous, calm, and happy may play a more important role in health than previously thought.

Okay, so if happiness improves health, how do we improve happiness? That’s the subject of my video Which Foods Increase Happiness?.

I’m as guilty as the rest of my colleagues for focusing on mental illness rather than mental health (though my Laughter as Medicine video is a rare exception). It’s a consequence of what’s out there in the medical literature, though I’ll make a special effort to highlight new studies in this area as they’re published. I do, however, have a number of videos on preventing and treating negative mood states, such as depression and anxiety:

What about psychiatric medications? See my videos Do Antidepressant Drugs Really Work?, Exercise vs. Drugs for Depression, and Saffron vs. Prozac.

Interested in other ways to improve our immune system? Check out Using the Produce Aisle to Boost Immunity.

In health,

Michael Greger, M.D.