The study, recently published in the Public Library of Science (PLOS) Journal of Medicine, found that globally, the prevalence of depression was 4.4 per cent, while Afghanistan and the Palestinian territories were amongst the most depressed states.
According to the research, depressive orders are second only to lower respiratory infections when it comes to inflicting the most years of disability on people throughout the world.
Clinical depression is defined as involving at least one major episode in which the affected individual experiences a depressed mood almost all day, every day for at least two weeks.
The researchers used data on the prevalence, incidence, remission rates and duration of depression and dysthymia (a milder, chronic form of depression that lasts for at least two years), and on the excess deaths caused by these disorders from published articles.
They found that the prevalence of depression for women was almost twice as high than it was for men.
More than five per cent of people in the Middle East, North Africa, Eastern Europe, sub-Saharan Africa and the Caribbean have depression, the researchers found.
Meanwhile, depression is lowest in East Asia, followed by Australia/New Zealand and Southeast Asia.
The researchers quantified the national "burden" of depression using a metric called DALY (disability-adjusted life years)– the number of healthy years a person loses because of depression or a depression-related premature death.
The burden is highest in Afghanistan and in Middle Eastern and North African countries.
"Our findings not only emphasize depressive disorders as a global health priority, but also highlight the importance of understanding the variations both between and within regions when setting global health objectives," wrote lead author Alize Ferrari, a researcher at Australia's University of Queensland, and colleagues.
"In the case of North Africa/Middle East, conflict in the region increased the prevalence of depression, leading to a higher burden ranking."
And as the conflict in Syria continues unabated, health officials are concerned depression rates, along with other psychological disorders common with the stress and trauma of war, will continue to rise.
In Lebanon, where there are more than 800,000 registered refugees, the International Medical Corps (IMC) said severe depression and anxiety were common.
"Though these disorders naturally exist within any given population, what has been observed from the specialists on the field is that amongst the Syrian population the severity of the disorders and the frequency by which they are appearing is higher in comparison to other communities where the environment is much more stable and secure," the IMC said.
"As such, daily stressors experienced by the majority of Syrian refugees renders those with pre-existing mental health disorders more susceptible to severe relapse and those who have a pre-disposition to develop a specific mental health illness, more vulnerable."
However, only a small number of refugees are receiving some form of mental support from the United Nations High Commission for Refugees (UNHCR) and other charities as organisations focus on basic needs such as food and shelter as winter approaches.
Meanwhile, in sub-Saharan Africa, the larger burden of communicable diseases such as HIV/AIDS and malaria resulted in a lower ranking.
The researchers also found the global burden of depressive disorders had increased over the years, due to longer life expectancy and population growth.
There was almost a 38 per cent increase in the global burden for depressive disorders between 1990 and 2010.
"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," they wrote.
However, it is important to note the research was based on the rate at which people were diagnosed with clinical depression, rather than actual rates of depression.
In other words, people who live in countries where there is greater access to mental health services are obviously more likely to be diagnosed at a higher rate.
That could explain the low rate of depression in a war-torn country such as Iraq where poor access to services could affect the rate at which depression is diagnosed. The stigma surrounding mental health could also explain low rates of depression in other regions such as East Asia.
And in cases where developing nations lacked data on depression, authors attempted to estimate rates.
As a result, the researchers said their findings most likely underestimated the true burden of depression.
They added that clinical depression was also linked to an increased risk of suicide and ischemic heart disease.
"These findings emphasise the importance of including depressive disorders as a public-health priority and implementing cost-effective inventions to reduce its burden," they concluded.
The views expressed in this article belong to the author and do not necessarily reflect the editorial policy of Middle East Monitor.