The glass can be half-full, or it can be half-empty, depending on your outlook on life – or on which side of the bed you get out of any particular morning. But can optimism or indeed pessimism really affect your health?
It's been a bone of contention for many years, and the issue has spawned a plethora of self-help guides on how to be "positive", especially in the face of serious illness. But the scientific evidence in support of a sunny disposition is contentious, contradictory and controversial.
The latest study comes from Finland, a land not noted for its joie de vivre. The conclusion of this research, published last week in BMC Public Health, found that pessimism was associated with an increased risk of death from coronary heart disease.
Of the 121 Finnish men and women who had died from coronary heart disease during the study's 11-year follow-up period – out of 2,267 participants – the researchers found a significant preponderance of pessimism when the study began. Comparing the higher and lower quartiles (the top and bottom 25%), people in the higher quartile for pessimism had a 2.2-fold higher risk of dying from heart disease than those in the lower quartile.
It seemed to support the idea that optimism is good for you. But hang on. There was a catch – because the researchers also looked at optimism in the same group of middle-aged Finns and failed to find any association with a decreased risk of coronary heart disease. So what's going on?
Well, one of the problems in previous studies on optimism and pessimism is that the two attitudes have been treated much like opposite ends of the same emotional spectrum. This produced conflicting results, according to the researchers, led by Mikko Pankalainen, a psychiatrist at the Paijat-Hame hospital in Lahti, southern Finland.
"People should not be categorised as optimists or pessimists," the researchers concluded. "Pessimism seems to be quite a significant risk factor for death from coronary heart disease both in men and women, while optimism does not protect from it."
It is not the first time that pessimism has been linked with ill health, although this study claims to be the first to link it negatively with coronary heart disease. "High levels of pessimism have previously been linked to factors that affect cardiac death, such as inflammation, but data on the connection between risk of death from coronary heart disease and optimism and pessimism as personality traits are relatively scarce," Pankalainen said.
But it must be emphasised that these studies only point to an association, rather than cause and effect. None can claim to show that being pessimistic actually causes someone to die prematurely.
Levels of pessimism could be measured "quite easily", Pankalainen said, by asking people to respond to a series of gloomy statements, such as "if something can go wrong for me, it will". Measuring optimism, on the other hand, relied on responses to statements such as "in uncertain times, I usually expect the best". When they carried out the statistical analysis on the two sets of outlooks, the researchers found no link between risk of heart deaths and optimism.
This runs contrary to a previous study of optimism, published in Stroke: Journal of the American Heart Association in 2011. It measured optimism levels on a 16-point scale in a "representative group" of just over 6,000 men and women and found that for every point increase in optimism, there was a corresponding 9% decrease in acute strokes over the two-year follow-up period.
"Our work suggests that people who expect the best things in life actively take steps to promote health," lead author Eric Kim of the University of Michigan said at the time. "Optimism seems to have a swift impact on stroke."
So the suggestion here was that optimistic people tended to look after themselves better than pessimistic individuals – so they perhaps had better diets and exercised more. However, there are no shortage of claims that optimism can also have a physical effect on the body by, for instance, boosting the immune system. One such study carried out on 124 law students in the US in 2010 showed how the immune response waxed and waned depending on a person's optimism or pessimism. Although there seems no getting away from the fact that most studies show that being optimistic can increase the chances of surviving with cancer, or improve the wellbeing of those with neurodegenerative conditions such as Parkinson's, the optimists do not always have it all their own way. At least one study has shown that older people with an optimistic outlook on life were more likely than pessimists to suffer disability and death within the following decade. Being grumpy when you are old may actually pay off.
And if you are a glass-half-empty person desperately trying to see it as half-full for the sake of your health, there is bad news from yet another study carried out in 2006, showing that we learn to be positive or negative in childhood. And one of the best ways of predicting a person's optimism turns out to be whether they were raised in a family where the parents were of a high socioeconomic status. Who said money isn't everything?
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