Ferrari, A.J., Charlson, F.J., Norman, R.E., Patten, S.B., Freedman, G., et al. (2013). Burden of depressive disorders by country, sex, age, and year: Findings from the global burden of disease study 2010. PLoS Medicine, 10(11): e1001547. doi:10.1371/journal.pmed.1001547.
Depressive disorders are among the most common mental disorders that previously were described as a leading cause of burden in the world. In epidemiological literature, burden is defined in several ways. One common metric is “disability adjusted life years” (DALYs) which represents loss of a healthy year of life. DALYs can be aggregated into the “years of life lived with disability” (YLD). Another metric is the “years of life lost due to premature mortality” (YLL). Each of these metrics of burden can be estimated from aggregating data from a number of studies and meta analyses that assess burden world wide. Such epidemiologic studies can also look at relative burden across countries, ages, and sex. In the 2000 Global Burden of Disease report, depressive disorders were the third leading cause of burden after lower respiratory infections and diarrhoeal diseases. Depression was also the leading cause of disability, responsible for 13.4% of years of life living with disability in women and 8.3% in men. In this study by Ferrari and colleagues, the authors provide a 2010 update to the Global Burden of Disease report for major depressive disorder and dysthymia. Major depressive episode is the experience of depressed mood almost all day, every day, for at least 2 weeks. Dysthymia involves a less severely depressed mood with duration of at least 2 years, a chronic rather than episodic course, but with low rates of remission. Ferrari and colleagues reviewed over 700 studies from 1980 to 2010. Prevalence (i.e., current rate) of major depression and dysthymia in the world population is 5.95%, representing nearly 400 million people. Major depression (4.4%) occurs more frequently than dysthymia (1.55%). Major depression occurs more frequently among women (5.5%) than men (3.2%). Major depression accounted for 8.2% of all years lost to disability, making it the second leading cause after low back pain. The percent of years lost due to disability increased since 1990, largely due to population increases and aging of the world population. The highest level of burden due to depression was seen in Afghanistan and the lowest in Japan. In terms of world regions, North Africa and Latin America showed the highest levels of burden due to depression. The authors also reported that 2.9% of disability adjusted life years from ischemic heart disease can be attributed to major depression.
This study joins others in past decades to define depression as a leading cause of years lost to disability worldwide, with over 400 million people suffering from a depressive disorder. The increasing burden of depression is partly due to decreasing mortality caused by other diseases in developing countries and population aging. Countries that have recently experienced conflict (e.g., Afghanistan, North Africa, Middle East) were particularly burdened by depression. But research has also linked depression to intimate partner violence and child sexual abuse. Mortality is elevated with major depression, as is disability related to other medical problems like heart disease. This epidemiological research points to the importance of identifying and treating depression in the population. Psychotherapeutic interventions provide highly effective treatments for depression.