OXFORD, England, Dec. 10 (UPI) -- Most people include happiness in their definition of a good life and think unhappiness is bad for them, but new research in England suggests neither has an effect on health or mortality.
Previous research has shown happiness is associated with a range of health conditions, including cardiovascular disease and disability levels, including a recent study showing head and neck cancer patients with depression had worse outcomes.
Researchers at the University of Oxford say, however, stress and misery do not lead to poor health outcomes, based on analysis of a study involving one million women in England, published in The Lancet.
"Illness makes you unhappy, but unhappiness itself doesn't make you ill," said Dr. Bette Liu, lead author of the study and now a professor at the University of New South Wales, in a press release. "We found no direct effect of unhappiness or stress on mortality, even in a ten-year study of a million women."
Oxford researchers considered data on 719,671 women with a median age of 59 who participated in the Million Women Study. The women joined the study between 1996 and 2001, with follow-up interviews conducted about 10 years after being recruited.
Of the women, 39 percent reported they were happy most of the time, 44 percent said they were usually happy, and 17 percent said they were unhappy. During the 10 years after initial surveys, 4 percent of the women died.
While self-reported poor health was strongly linked to unhappiness, researchers adjusted for hypertension, diabetes, asthma, arthritis, depression, anxiety, and lifestyle factors such as smoking, deprivation, and BMI -- finding unhappiness was not associated with mortality from any cause.
In an editorial published in The Lancet with the study, researchers acknowledge gaps in the study, such as the effects of unhappiness on cognitive disorders and the ways happiness affects development during childhood.
Because of several studies showing happiness and unhappiness affect health, especially in the last two decades, researchers said randomized, controlled trials need to be held with healthy and clinical patients in order to determine happiness level's actual effect on health.