There is growing evidence that psychologically healthier people have a decreased chance of being sick. Studies show happier people tend to get sick less and do better when sick. Positive moods are associated with less stress and inflammation and better fights against infection. But that could mean positive people just live healthier lifestyles. Happy people smoke less, exercise more, drink less and sleep better.
In a study that showed same level of smoking, drinking, exercise and sleep for both healthy and depressed, happier people seem to live longer.
A study decided to test 334 healthy volunteers with the common cold virus. They were asked how happy, relaxed and pleased they were, or how anxious, hostile and depressed. They were given nasal drops of the cold virus to see who would get the cold, and whose immune system would fight it off. 33 percent of the sadder people go the cold, while only 20 percent of the happy people got the cold. Both groups had same exercise, sleep and supplements, and happier people just showed a better resistance to the cold.
They repeated the same study with the flu and got similar results.
Watch video of sourced information below, from NutritionFacts.org.