Science is increasingly suggesting a link between happiness and health.

There is an irrefutable argument in favor of happiness: Happiness and good health go hand-in-hand. In fact scientific studies have been finding that happiness can make our hearts healthier, our immune systems stronger, and our lives longer through enhancements of our cellular structure.

Dr Derek Cox, Director of Public Health at Dumfries and Galloway NHS, suspects that for decades health professionals have been missing a big trick in improving the health of the nation.

“We’ve spent years saying that giving up smoking could be the single most important thing that we could do for the health of the nation.

“And yet there is mounting evidence that happiness might be at least as powerful a predictor, if not a more powerful predictor than some of the other lifestyle factors that we talk about in terms of cigarette smoking, diet, physical activity and those kind of things.”

5 Ways Happiness Affects Your Cellular Structure

1) Protects Our Heart 

A 2005 paper found that happiness predicts lower heart rate and blood pressure. In the study, participants rated their happiness over 30 times in one day and then again three years later. The initially happiest participants had a lower heart rate on follow-up (about six beats slower per minute), and the happiest participants during the follow-up had better blood pressure.

In a 2010 study, researchers invited nearly 2,000 Canadians into the lab to talk about their anger and stress at work. Observers rated them on a scale of one to five for the extent to which they expressed positive emotions like joy, happiness, excitement, enthusiasm, and contentment. Ten years later, the researchers checked in with the participants to see how they were doing — and it turned out that the happier ones were less likely to have developed coronary heart disease. In fact, for each one-point increase in positive emotions they had expressed, their heart disease risk was 22 percent lower.

2) Enhances Our Immune System

Happy people, as compared with less happy people, tend to have greater immune system functioning, a reduced risk of cardiovascular disease, and report greater marriage and job satisfaction. It is therefore valuable to develop a deeper understanding of the positive affect by investigating its biological basis. Several studies have begun to investigate potential biological markers of positive affect.

In a 2003 experiment, 350 adults volunteered to get exposed to the common cold (don’t worry, they were well-compensated). Before exposure, researchers called them six times in two weeks and asked how much they had experienced nine positive emotions — such as feeling energetic, pleased, and calm — that day. After five days in quarantine, the participants with the most positive emotions were less likely to have developed a cold.

Some of the same researchers wanted to investigate why happier people might be less susceptible to sickness, so in a 2006 study they gave 81 graduate students the hepatitis B vaccine. After receiving the first two doses, participants rated themselves on those same nine positive emotions. The ones who were high in positive emotion were nearly twice as likely to have a high antibody response to the vaccine — a sign of a robust immune system. Instead of merely affecting symptoms, happiness seemed to be literally working on a cellular level.

3) Combats Cortisol and Stress

To protect the brain from stress, happiness releases a protein called BDNF (Brain-Derived Neurotrophic Factor) which has a protective and also reparative element to memory neurons and acts as a reset switch. That’s why we often feel so at ease and things are clear after moments of stress and eventually happy.

Happiness also seems to carry benefits even when stress is inevitable. In a 2009 study, some diabolically cruel researchers decided to stress out psychology students and see how they reacted. The students were led to a soundproof chamber, where they first answered questions indicating whether they generally felt 10 feelings like enthusiasm or pride. Then came their worst nightmare: They had to answer an exceedingly difficult statistics question while being videotaped, and they were told that their professor would evaluate their response. Throughout the process, their heart was measured with an electrocardiogram (EKG) machine and a blood pressure monitor. In the wake of such stress, the hearts of the happiest students recovered most quickly.

4) More Prone to Optimistic Thought Patterns

Neuroscientists have discovered that people who have a more cheerful disposition and are more prone to optimism generally have higher activity occurring in their left PFC. But that’s a brain explanation. Interestingly, behavioral scientists have observed fascinating differences between optimists and pessimists. Optimism, for example, involves highly desirable cognitive, emotional, and motivational components. Optimistic people tend to have better moods, to be more persevering and successful, and to experience better physical health.

A 2005 study suggests that positive emotion also mitigates pain in the context of disease. Women with arthritis and chronic pain rated themselves weekly on positive emotions like interest, enthusiasm, and inspiration for about three months. Over the course of the study, those with higher ratings overall were less likely to experience increases in pain.

5) Lengthens Our Lives

In the end, the ultimate health indicator might be longevity — and here, especially, happiness comes into play. In perhaps the most famous study of happiness and longevity, the life expectancy of Catholic nuns was linked to the amount of positive emotion they expressed in an autobiographical essay they wrote upon entering their convent decades earlier, typically in their 20s. Researchers combed through these writing samples for expressions of feelings like amusement, contentment, gratitude, and love. In the end, the happiest-seeming nuns lived a whopping 7-10 years longer than the least happy.

You don’t have to be a nun to experience the life-extending benefits of happiness, though. In a 2011 study, almost 4,000 English adults ages 52-79 reported how happy, excited, and content they were multiple times in a single day. Here, happier people were 35 percent less likely to die over the course of about five years than their unhappier counterparts.

These two studies both measured specific positive emotions, but overall satisfaction with one’s life — another major indicator of happiness — is also linked to longevity. A 2010 study followed almost 7,000 people from California’s Alameda County for nearly three decades, finding that the people who were more satisfied with life at the beginning were less likely to die during the course of the study.

As the science of happiness and health matures, researchers are trying to determine what role, if any, happiness actually plays in causing health benefits. They’re also trying to distinguish the effects of different forms of happiness (including positive emotions and life satisfaction), the effects of “extreme” happiness, and other factors. For example, a new study suggests that we should look not just at life satisfaction levels but life satisfaction variability: Researchers found that low life satisfaction with lots of fluctuations — i.e., an unstable level of happiness — was linked to even earlier death than low life satisfaction alone.