Clinical depression is now the second-leading cause of global disability, according to new research, with the highest rates of incidence affecting working-age adults and women more than men.
In a paper published Tuesday in the journal Plos Medicine, researchers found that depressive disorders were second only to lower respiratory infections when it came to inflicting the most years of disability on people throughout the world.
Rates of depression were highest in Afghanistan and lowest in Japan, while the condition ranked as the top cause of disability in Central America and Central and Southeast Asia.
Authors reviewed a variety of published epidemiological studies before calculating that the global prevalence of depression was 4.4%. Authors wrote that the rate for women, 5.5%, was higher than it was for men, 3.2%.
"These findings reinforce the importance of treating depressive disorders as a public-health priority and of implementing cost-effective interventions to reduce their ubiquitous burden," wrote lead author Alize Ferrari, a researcher at Australia's University of Queensland, and colleagues.
In cases where poor or developing nations lacked data on depression, authors attempted to estimate rates.
Clinical depression, or major depressive disorder, involves at least one major episode in which the sufferer experiences overwhelming feelings of sadness and hopelessness nearly all day, every day, for two weeks. Researchers also found that the disorder was associated with increased risk of suicide as well as ischemic heart disease.
Researchers also examined rates for dysthymia, a milder, chronic form of depression that lasts for at least two years.
The so-called global burden of depressive disorders has been increasing steadily over the years, due to population growth and longer life expectancy, according to study authors. Between 1990 and 2010, the global burden for depressive disorders increased by almost 38%, authors wrote.
"This has important implications for global health, especially in developing countries where increased life expectancy due to better reproductive health, nutrition, and control of childhood infectious diseases means more of the population are living to the age where depressive disorders are prevalent," authors said.