There are several studies which indicate that enhanced happiness leads to improved health. The most thorough study
was done by the Department of Labour in Australia and analyzed and published in the American Journal of Health Promotion by Siahpush, Spittal and Singh. They looked at two representative population-based samples of 9981 people surveyed in 2001 and 2004. They examined the relationship between happiness in 2001 and their health in 2004. In 2001, they used the question about happiness that we copied, and corrected their calculations for health problems noted in that year.