The Washington Post reports on a new study that reveals the prevalence of depression around the world.  Researchers at Australia’s University of Queensland found that the Middle East and North Africa suffer the world’s highest depression rates.  Globally, depression is the second-leading cause of disability, with slightly more than 4 percent of the world’s population diagnosed with it.  The article reports that 

the most depressed country is Afghanistan, where more than one in five people suffer from the disorder. The least depressed is Japan, with a diagnosed rate of less than 2.5 percent.

What accounts for the higher rates of depression in certain countries?  Researchers theorize that military conflict is one important cause.  The article also points to a 2010 paper by the Inter-American Development Bank which found that unemployment, low incomes and high income inequality correlate with high depression rates.  Finally, there is the age factor.  Studies have shown that people between 16 and 65 tend to suffer depression at much higher rates.

That age factor, along with massive population growth, actually explains the fact that the burden of depression has grown by nearly a third since 1990.  And since both aging and population growth are likely to continue, that makes low-cost depression interventions even more of a priority for both global organizations and national governments.