© Live ScienceSad older man.
Depression is more likely to strike in high-income countries than in poor ones, according to new research on depression rates across 18 countries worldwide.
The study, published July 25 in the
open-access journal BMC Medicine, found that the average lifetime prevalence of major depression in the 10 high-income countries in the study was 14.6 percent. In the eight low- and middle-income countries, the lifetime prevalence of major depression was 11.1 percent.
Across countries, depression was linked to social factors such as age, marital status and income, though sometimes in complicated ways. In low-income and middle-income countries, for example, the average age of a
first depressive episode was 24. In high-income countries, depression was likely to hit almost two years later, at 25.7.
The researchers speculate the wealthier countries experience more of the blues because richer countries also have more income inequality. In addition, depression may be a disease of the affluent, a phenomenon that isn't fully understood, they say. Figuring out the causes of depression around the world will help initiatives to combat the mental-health problem, which has been linked to
Alzheimer's disease. In severe cases, depression can end in suicide, which leads to about 850,000 deaths per year, according to the World Health Organization (WHO).