Recent science has shown how important our minds are to our bodies, but they also reveal how difficult it is to define and promote happiness.
Every day there are new studies linking our mental health to our physical health. Our moods or mental states - positive, neutral, negative - seem to be related to the risk of disease, and indeed, our likelihood of death.
Just last month, for example, a study reported that cardiovascular health is significantly better in people who report being happier. On one level, there is an obvious explanation to the phenomenon: Happy people are more likely to engage in the healthy behaviors - exercise and eating right - that lead to good hearts in the first place. While this relationship may have a lot of explanatory power, the plot seems to be thicker than this.
Are "happy" people set up differently to begin with? For example, their physiologies seem to be different from those of less happy people, with lower levels of the stress hormone cortisol, reduced inflammatory biomarkers, and even changes in the wiring of the brain. All of these differences might make happy people better able to deal with the adverse events that life throws at them, and less likely to feel the effects of stress, which takes a toll on everybody's health. The happiness-health relationship is at the very least a two-way street.
Psychologists have debated for a while about whether happiness and unhappiness are two sides of the same coin, or whether they're unique entities.
But what is happiness in the first place? Is it about seeking out activities that make us feel good - indulging a fancy car or going out for a satisfying dinner - or does it have to do with a deeper sense of personal satisfaction over the course of a lifetime?
It's this question that may be at the heart of the matter. The kind of happiness you experience - and seek - may matter most to your health. In fact, it may be what defines it. There's a lot we still have to learn about how our heads contribute to bodily health, but here's what we know about the relationship so far.
DEFINING HAPPINESS ISN'T SO EASY
As most people have probably experienced, there are different types of "happy." There's the happiness we get from buying a new iPad and there's the happiness we get from having a fulfilling job that lets us buy the iPad. This fundamental difference is one that researchers have tried to tease apart, and they've described two distinct forms of happiness.
"Hedonic" happiness has to do with pleasure and being satisfied in an immediate sense ("hedonism," of course, comes from the same root). It's about how often you feel good, and experience feelings like excitement, interest, and enthusiasm.
People who are higher in eudaimonic, or long-term, happiness have reduced biomarkers of inflammation, like interleukin-6.
"Eudaimonic" well being, on the other hand, has to do with being satisfied with life in a larger sense; it's about "fulfilling one's potential and having purpose in life," explains Julia Boehm, who studies the relationship between happiness and health at Harvard. How autonomous or self-sustaining you feel, how interested you are in personal growth, the nature of your relationships with other people, whether you have a deep purpose in life, and your degree of self-acceptance are some of the variables that researchers try to measure to get a good idea of whether a person has eudaimonic happiness.
Some scientists have studied the two forms of happiness in the lab and found some significant differences. Work at the University of Wisconsin has found that people who are higher in eudaimonic happiness have reduced biomarkers of inflammation, like interleukin-6. These biomarkers, according to researcher Carol Ryff, are linked to a number of health problems like metabolic syndrome, diabetes, and cardiovascular disease, so lower levels of them might offer a protective benefit. Ryff has also found that having a strong social support network - an integral part of long term life satisfaction - is connected with lower levels of the same biomarkers.
Eudaimonic happiness (or we could call it personal or inner satisfaction) may even help set up the brain differently. Hedonic or short-term happiness has more to do with the kind of "feel good" behaviors that light up the "reward circuits" of the brain, which rely on the neurotransmitter dopamine. These areas are also important in addictive behaviors, which makes sense, since satisfying an addictive craving is the ultimate form of short term (hedonic) pleasure.
On the other hand, when people who are happy in a deeper way (have more long-term, eudaimonic happiness), are faced with negative stimuli, they have more activity in the prefrontal cortex of the brain, which governs executive planning and higher-level thinking. They also have reduced activity in "lower" brain regions, like the amygdala, the seat of our stress and fear responses. People with eudaimonic happiness are also slower to evaluate negative events as being such, which could mean that they are also less likely to "freak out" over real upsets in life.
Do Definitions Matter? Yes.
Some researchers aren't so sure that the two concepts need to be separated - and that one good definition of happiness could be sufficient. Boehm says that she prefers the term "positive psychological well-being" over eudaimonic happiness, because, as she says, "It captures a broad range of terms including happiness, purpose in life, optimism, life satisfaction, etc... It can be characterized by the positive feelings, thoughts, and expectations that a person has for his or her life. Essentially, positive psychological well-being is an indicator of psychological functioning that goes beyond the mere absence of disease, e.g., depression, anxiety." (More on this shortly.)