For people in Japan, happiness isn’t associated with better health

Feeling positive emotions is good for your physical health, right? There's certainly evidence in support of the idea. But it's mostly come from studies of people living in Western countries. Now a study published in Psychological Science, concludes that for people in Japan, it may not be the case.

While positive emotions, like happiness, are seen as a good thing in the US, UK, and elsewhere in Europe, the picture is different in east Asia: they aren't seen being as necessarily desirable, and negative emotions aren't considered to be all that bad. As the researchers, led by Jiah Yoo at the University of Wisconsin-Madison, US, write in their introduction: "No study to date has directly compared the biological correlates of positive affect across cultures."

The researchers studied 1,017 men and women living in America, and 374 men and women in Japan (selected to be representative of the general population). The participants rated how frequently they had felt each of 10 positive emotions over the past 30 days (including happiness, cheerfulness, "calm and peaceful", "full of life" and proud). They also gave blood samples, which were checked for levels of HDL-cholesterol ("good" cholesterol) and LDL-cholesterol ("bad" cholesterol). An unhealthy cholesterol profile increases the risk of heart disease – the world's biggest killer – but can be improved through exercise and healthy eating, for example.

The researchers controlled statistically for the influence of age, gender and years of education – all known to be linked to cholesterol profiles – and negative emotions over the past month (to be sure that positive emotions were associated with cholesterol independently of these demographic factors or negative emotions). They also measured participants' smoking, alcohol consumption, healthy eating, and body mass index (BMI) to see if these were relevant to any potential links between emotion and cholesterol levels.

For the Americans in the study, experiencing higher levels of positive emotions was indeed associated with having a healthier cholesterol profile, so much so, in fact, as to be clinically significant. But there was no such association whatsoever for the Japanese.

When the researchers dug further into the data they found that the cultural difference in the association between positive emotions and cholesterol was, to a large extent, related to body mass index (BMI). Americans, but not Japanese, who felt more positive emotions also tended to have a lower BMI, which might explain their lower cholesterol – people who are not overweight generally have a healthier cholesterol profile. There was also evidence that Americans who had a lower BMI and felt more positive emotions did more exercise.

The researchers concluded: "These results are consistent with a theoretical prediction that a good fit between one's emotions and one's culturally prescribed values and beliefs may motivate a healthier lifestyle. Frequent experience of positive affect in the Western context would be aligned with prescribed values and beliefs and thus likely motivate engagement in and pursuit of healthy behaviours."

However, there are other possible explanations. For example, perhaps Americans who exercise are more likely to feel more positive emotions, be of healthy weight, and therefore enjoy a healthier cholesterol profile.

Extrapolating from national data, only 3.6 per cent of the Japanese participants would have been obese, compared with 32 per cent of the Americans. With less variation in BMI in the Japanese sample, it would have been harder to spot any links between BMI and positive emotion. While the researchers argue that differences in cultural attitudes to positive emotion explain their data, more research is certainly needed to support their interpretation.