Burden of Depressive Disorders by Country, Sex, Age, and Year: Findings from the Global Burden of Disease Study 2010

Abstract

In this paper, Ferrari and colleagues analyzed the burden of depressive disorders in GBD 2010 and identified depressive disorders as a leading cause of burden. The authors present severity proportions; burden by country, region, age, sex, and year; as well as burden of depressive disorders as a risk factor for suicide and ischemic heart disease.

Please see later in the article for the Editors' Summary

Abstract

Background

Depressive disorders were a leading cause of burden in the Global Burden of Disease (GBD) 1990 and 2000 studies. Here, we analyze the burden of depressive disorders in GBD 2010 and present severity proportions, burden by country, region, age, sex, and year, as well as burden of depressive disorders as a risk factor for suicide and ischemic heart disease.

Methods and Findings

Burden was calculated for major depressive disorder (MDD) and dysthymia. A systematic review of epidemiological data was conducted. The data were pooled using a Bayesian meta-regression. Disability weights from population survey data quantified the severity of health loss from depressive disorders. These weights were used to calculate years lived with disability (YLDs) and disability adjusted life years (DALYs). Separate DALYs were estimated for suicide and ischemic heart disease attributable to depressive disorders.

Depressive disorders were the second leading cause of YLDs in 2010. MDD accounted for 8.2% (5.9%–10.8%) of global YLDs and dysthymia for 1.4% (0.9%–2.0%). Depressive disorders were a leading cause of DALYs even though no mortality was attributed to them as the underlying cause. MDD accounted for 2.5% (1.9%–3.2%) of global DALYs and dysthymia for 0.5% (0.3%–0.6%). There was more regional variation in burden for MDD than for dysthymia; with higher estimates in females, and adults of working age. Whilst burden increased by 37.5% between 1990 and 2010, this was due to population growth and ageing. MDD explained 16 million suicide DALYs and almost 4 million ischemic heart disease DALYs. This attributable burden would increase the overall burden of depressive disorders from 3.0% (2.2%–3.8%) to 3.8% (3.0%–4.7%) of global DALYs.

Conclusions

GBD 2010 identified depressive disorders as a leading cause of burden. MDD was also a contributor of burden allocated to suicide and ischemic heart disease. These findings emphasize the importance of including depressive disorders as a public-health priority and implementing cost-effective interventions to reduce its burden.

Please see later in the article for the Editors' Summary

Editors' Summary

Background

Depressive disorders are common mental disorders that occur in people of all ages across all world regions. Depression—an overwhelming feeling of sadness and hopelessness that can last for months or years—can make people feel that life is no longer worth living. People affected by depression lose interest in the activities they used to enjoy and can also be affected by physical symptoms such as disturbed sleep. Major depressive disorder (MDD, also known as clinical depression) is an episodic disorder with a chronic (long-term) outcome and increased risk of death. It involves at least one major depressive episode in which the affected individual experiences a depressed mood almost all day, every day for at least 2 weeks. Dysthymia is a milder, chronic form of depression that lasts for at least 2 years. People with dysthymia are often described as constantly unhappy. Both these subtypes of depression (and others such as that experienced in bipolar disorder) can be treated with antidepressant drugs and with talking therapies.

Why Was This Study Done?

Depressive disorders were a leading cause of disease burden in the 1990 and 2000 Global Burden of Disease (GBD) studies, collaborative scientific efforts that quantify the health loss attributable to diseases and injuries in terms of disability adjusted life years (DALYs; one DALY represents the loss of a healthy year of life). DALYs are calculated by adding together the years of life lived with a disability (YLD, a measure that includes a disability weight factor reflecting disease severity) and the years of life lost because of disorder-specific premature death. The GBD initiative aims to provide data that can be used to improve public-health policy. Thus, knowing that depressive disorders are a leading cause of disease burden worldwide has helped to prioritize depressive disorders in global public-health agendas. Here, the researchers analyze the burden of MDD and dysthymia in GBD 2010 by country, region, age, and sex, and calculate the burden of suicide and ischemic heart disease attributable to depressive disorders (depression is a risk factor for suicide and ischemic heart disease). GBD 2010 is broader in scope than previous GBD studies and quantifies the direct burden of 291 diseases and injuries and the burden attributable to 67 risk factors across 187 countries.

What Did the Researchers Do and Find?

The researchers collected data on the prevalence, incidence, remission rates, and duration of MDD and dysthymia and on the excess deaths caused by these disorders from published articles. They pooled these data using a statistical method called Bayesian meta-regression and calculated YLDs for MDD and dysthymia using disability weights collected in population surveys. MDD accounted for 8.2% of global YLDs in 2010, making it the second leading cause of YLDs. Dysthymia accounted for 1.4% of global YLDs. MDD and dysthymia were also leading causes of DALYs, accounting for 2.5% and 0.5% of global DALYs, respectively. The regional variation in the burden was greater for MDD than for dysthymia, the burden of depressive disorders was higher in women than men, the largest proportion of YLDs from depressive disorders occurred among adults of working age, and the global burden of depressive disorders increased by 37.5% between 1990 and 2010 because of population growth and ageing. Finally, MDD explained an additional 16 million DALYs and 4 million DALYs when it was considered as a risk factor for suicide and ischemic heart disease, respectively. This “attributable” burden increased the overall burden of depressive disorders to 3.8% of global DALYs.

What Do These Findings Mean?

These findings update and extend the information available from GBD 1990 and 2000 on the global burden of depressive disorders. They confirm that depressive disorders are a leading direct cause of the global disease burden and show that MDD also contributes to the burden allocated to suicide and ischemic heart disease. The estimates of the global burden of depressive disorders reported in GBD 2010 are likely to be more accurate than those in previous GBD studies but are limited by factors such as the sparseness of data on depressive disorders from developing countries and the validity of the disability weights used to calculate YLDs. Even so, 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.

Additional Information

Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001547.

• The US National Institute of Mental Health provides information on all aspects of depression

• The UK National Health Service Choices website also provides detailed information about depression and includes personal stories about depression

• More personal stories about depression are available from healthtalkonline.org

• MedlinePlus provides links to other resources about depression (in English and Spanish)

• The World Health Organization provides information on depression and on the global burden of disease (in several languages)

• Information about the Global Burden of Disease initiative is available

• beyondblue provides many resources on depression

• The Queensland Centre for Mental Health Research provides information on epidemiology and the global burden of disease specifically for mental disorders