A large new study of women in the UK refutes a widespread belief that unhappiness itself can cause ill health.

Indeed, say researchers, life-threatening poor health can lead to unhappiness, hence the association with increased mortality, but unhappiness itself does not appear to be a cause.

The research team sent women involved in the UK Million Women Study a questionnaire in which they were asked to rate their health, happiness, stress, and feelings of control and relaxation. Five out of six said they were generally happy.

Unhappiness was found to be associated with deprivation, smoking, lack of exercise and not living with a partner, but it was women who were already in poor health who were most likely to report being unhappy, stressed, not in control and not relaxed.

The main analyses included 700,000 women, average age 59, who were followed over 10 years, during which 30,000 died.

After allowing for health and lifestyle differences, the overall death rate among those who were unhappy was the same as the death rate among those who reported being happy.

Lead author Dr. Bette Liu, now at the University of New South Wales, Australia, explained: "Illness makes you unhappy, but unhappiness itself doesn't make you ill. We found no direct effect of unhappiness or stress on mortality."

The study was published in The Lancet.