Distinguished Professor Evelyn Bromet, PhD led a team of researchers in an international study that compared rates of depression in countries from around the globe, including both high, middle, and low income countries. Their findings were published in BMC Medicine on July 26, 2011.
After conducting face-to-face interviews with 89,037 adults in 18 countries as part of the World Health Organization’s World Mental Health Survey, the researchers estimated that 14.6% of people in wealthier countries and 11.1% of people in poorer countries have experienced a major depressive episode sometime during their lifetime. When they looked at the percentages of people who reported a major depressive episode during the 12 months preceding the interview, they estimated that that 5.5% of people in wealthier countries and 5.9% of people in poorer countries experienced an episode within the past year.
About half the people interviewed said that at some time in their lives they had experienced an episode of being sad or depressed or losing interest in their usual activities which lasted for several days.
The researchers found a broad range of lifetime prevalence rates across the countries included in the study, from lows of 6.5% in China and 6.6% in Japan to highs of 19.2% in the United States and 21.0% in France. Consistent with earlier studies, they found that the rate of depression among women is about twice that of men and that people who are separated or divorced have higher rates of depression than people who are currently married. They also found that major depression is associated with substantial impairment, so much so that the average level of impairment was approximately 5 to 8 times higher among people who were currently experiencing major depression than those who were not.
Careful analysis of the data led Dr. Bromet and her colleagues to conclude that the variance in results across countries is probably due to actual differences in rates of depression, rather than biases introduced by the sampling method, although they were unable to identify the reasons for the differences in rates. The fact that there was a disparity in lifetime prevalence rates between richer and poorer countries while the 12-month prevalence rates were almost identical led them to speculate that people living in lower income counties may have more difficulty recalling or reporting earlier episodes of depression.
The authors conclude that their results “confirm the public-health importance of major depression as a commonly occurring and seriously impairing condition with a generally early age of onset and persistent course in a wide range of countries.”
Dr. Bromet heads the Epidemiology Research Group of the Department of Psychiatry and Behavioral Science at Stony Brook University. Twenty-one additional researchers co-authored the paper. Professor Ronald Kessler at Harvard University initiated and directs the World Mental Health Survey Consortium.
