Economic progress in many developing countries is often accompanied by increased air pollution and this, in turn, is contributing to higher levels of depression, a new study led by the Yale School of Public Health finds.
The discovery contributes to the growing field of happiness economics, which quantifies the economic impact of personal well-being and life satisfaction, which are increasingly factored into policy-making decisions worldwide.
China’s increase in air pollution accounts for 22.5 percent of the actual decline in happiness in the country from 2007 to 2014, the study finds. In particular, those who are more concerned with environmental problems, work outdoors, earn lower incomes, or have young children are emotionally more sensitive to air pollution.
“Air pollution heavily influences mental and emotional states. It heightens social inequality and is an important factor in a person’s sense of their overall welfare,” said Assistant Professor Xi Chen, Ph.D., lead author of the study in the Journal of Environmental Economics and Management.
The research provides support to the Easterlin paradox, a concept in happiness economics which proposes that happiness does not correlate with economic growth, even though the rich are found to be happier than the poor at any given time. The study warns that GDP-obsessed development strategy in many fast growing economies in the world, such as India and China, may not bring about improved happiness.
This study shows for the first time that worsening air quality can be a key factor for reduced happiness amid rapid economic growth, which still puzzles scholars and policymakers. The study also offers the first population level evidence that air pollution is a major risk factor of depressive symptoms, and that the psychological costs of air pollution are well underestimated.
Chen and his team compared a national longitudinal survey on happiness in China, with air quality and weather information captured at the exact moments respondents were surveyed. The environmental data Chen used looked at levels of air pollutants, including particulate matter (PM), sulfur dioxide and nitrogen dioxide, as well as air temperature and precipitation in the time and geographical location in which interviews took place.
China is an ideal location for examining the Easterlin paradox in this novel way. According to Easterlin, in spite of unprecedented income growth, China’s average happiness did not improve from 1990 to 2010. The World Bank also places 16 of the world’s top 20 most polluted cities in China.
Previous studies attempting to connect air pollution and mental health have stumbled on finding reliable measurements of each; other methods, such as the use of aggregate data or cross-sectional data are prone to biases that compromise results. Using longitudinal data captures the effect of changes in air quality on the same set of people over time, strengthening the link between the two.
Chen’s novel methods were also able, unlike in previous studies, to distinguish between hedonistic happiness, or happiness that varies from moment to moment, and evaluative happiness, which is equated with overall life satisfaction. The results showed that while air pollution had a major impact on hedonistic happiness, it caused little change to measures of life satisfaction.
The study also sheds light on the impact of air pollution on a wide range of economic topics, and indicates that not enough weight is given to the ill effects of air pollution when measuring
factors such as worker productivity. While few studies exist that evaluate the social and economic effects of air pollution in low-income countries, Chen’s work contributes to the literature by adding air pollution to the list of risk factors for depression in the part of the world. Further research is needed into rates of depression in these countries, to understand the extent and impact of mental illness in the developing world.
Chen worked with Xiaobo Zhang, chair and professor of economics, and Ph.D. candidate, Xin Zhang, both of the National School of Development at Peking University in China, on the study.