Whether you've got a runny nose, a broken leg, or a chronic disease, if you’re like me you’ve lost count of the number of times you’ve been told to “cheer up,” “look on the bright side” and “think positive thoughts” in order to get better faster. Talk shows, magazine articles, and self help gurus only reinforce this idea, so it’s little wonder that many of us believe that being positive can make us healthier.

As a health journalist who has been diagnosed with a chronic illness, I wanted to delve into the scientific evidence to see if there is any actual proof of a link between positive emotions and health. Fortunately, a researcher who has dedicated her career to exploring this topic was happy to talk me through it all over a long conversation on Skype.

Associate professor Sarah Pressman runs the STEP (Stress, Emotion, and Physical Health) lab at the University of California, Irvine. Back in 2005, Pressman joined with a leading emotions researcher, Sheldon Cohen from Carnegie Mellon University, in order to pour over the scientific literature and determined whether good feelings like joy and contentment are truly linked to good health. Their review found that people who have a more positive outlook do tend to feel healthier. “So if you ask them, ‘How do you feel?’ they're going to say they feel healthier. They’re going to feel that they are in less pain and report fewer symptoms. Even if you control for things like how severe their illness is, or how healthy they are objectively, you still see that kind of subjective difference,” Pressman told me.

So, based on this, we’ve known for some time that positive emotions might help you cope and feel better about your illness, but can they actually make you healthier?

Certainly there is a mountain of research linking positive emotions such as joy, love, hope, wonder, and awe to good health. For example, a study that followed more than 6000 university students for more than 40 years found that pessimistic students tended to die younger than their optimistic peers. A 2011 review of more than 160 studies found “clear and compelling evidence” that people who have positive dispositions tend to live longer and experience better health than negatively-inclined people. The reviewers estimated that when all was said and done, having higher levels of positive emotions may add 4-10 years to your life. There’s also a connection between positive emotions and your susceptibility to catching the common cold. As I’ve written about before, when Pressman’s health-emotions research colleague, Sheldon Cohen, quarantined people in a hotel room for five days and exposed them to the rhinovirus (the common cold virus), he found that positive people were less likely to get sick.

When you think about why this might be, the answers seem pretty obvious. Optimists are more likely to take proactive steps to protect their health. Sunny side uppers are probably more likely to eat healthier foods, exercise more, have good friends, strong support networks and less chronic stress. Being more likeable may also endear you to your doctors and get them to pay more attention to you. But what’s interesting about Cohen’s flu study is that positivity correlated with a lower risk of getting a cold independently of healthy behaviours and other factors such as age, weight, gender, and whether a person was already immune to the virus. He has even replicated the findings.

This has lead Pressman and her emotions-health research comrades to see if positive emotions may somehow be able to “get under the skin” and interact with our immune and other biological systems to influence our health. In one fascinating study, Pressman gave willing volunteers a minor skin wound by putting adhesive tape on their arms and then ripping it off about 50 times. She reported that people with higher levels of positivity healed more quickly than those with less positive outlooks. When you think about it, these findings have some big implications. “If you’re seriously injured or have had surgery, you want to heal quickly because the amount of time it takes you to heal can influence whether or not you get secondary infections or whether you get injured again,” Pressman said.

Barbara Fredrickson, a psychology professor at the University of North Carolina, Chapel Hill believes that one of the reasons for the beneficial physiological effects of positive emotions is that they may have an ‘undoing’ effect. In one experiment, Fredrickson demonstrated that people with higher levels of positive emotions can recover faster from stress. She told 57 people they would have to deliver an impromptu speech about why they’re a good friend in front of a hostile panel and video camera and looked at their cardiovascular measurements. She found that people who were more positive were also more resilient physiologically and bounced back from the threat of the speech task faster.

Like with so much that I write about on this blog, all this comes with a big caveat. There is no evidence suggesting negative emotions cause illness, or that disease arises from some kind of innate personality defect, or even that something like psychotherapy can stop the progression of cancer or heart disease. “Our take on it is that there is an upper limit; that there are these physiological and behavioural things that positive emotions can do for us, but that one of the things they can't do is build you a new kidney if your kidney fails,” said Pressman who cautions that we need to be realistic about what positivity can do.

There’s also some evidence to suggest that being overly positive makes no difference to outcomes for people who are already seriously sick. In fact, people with end-stage disease and diseases from which they are likely to die quickly may be harmed by high levels of positivity. According to Pressman, this too makes sense. “If you think, "Oh, I'm going to beat this illness," then maybe you're not being as diligent in terms of reporting changes in your symptoms to your doctor. You might not be adhering to your medication as closely, or you might not be following up as often as you should. A little bit of negativity could potentially be a good thing in that context, because it makes you really focus in on your illness and how you're going to fight it. That can be important,” she said.

With my caveat out of the way, even the most critical of skeptics must acknowledge that there is now clear evidence that the functions of our mind do influence the health of our body. Whether through positivity exercises, meditation, psychotherapy or just having a good old natter with a close friend, attending to our emotions is a fundamental necessity when we want to get healthy.

Listen to my conversation with Sarah Pressman PhD in Epsiode 2 of The Whole Health Life podcast: