a1 The University of Queensland, School of Population Health, Herston, QLD, Australia
a2 Queensland Centre for Mental Health Research, The Park Centre for Mental Health, Wacol, QLD, Australia
a3 The University of Queensland, Institute of Social Science Research, St Lucia, QLD, Australia
a4 The University of Queensland, Queensland Children's Medical Research Institute, Herston, QLD, Australia
a5 Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada
Background Summarizing the epidemiology of major depressive disorder (MDD) at a global level is complicated by significant heterogeneity in the data. The aim of this study is to present a global summary of the prevalence and incidence of MDD, accounting for sources of bias, and dealing with heterogeneity. Findings are informing MDD burden quantification in the Global Burden of Disease (GBD) 2010 Study.
Method A systematic review of prevalence and incidence of MDD was undertaken. Electronic databases Medline, PsycINFO and EMBASE were searched. Community-representative studies adhering to suitable diagnostic nomenclature were included. A meta-regression was conducted to explore sources of heterogeneity in prevalence and guide the stratification of data in a meta-analysis.
Results The literature search identified 116 prevalence and four incidence studies. Prevalence period, sex, year of study, depression subtype, survey instrument, age and region were significant determinants of prevalence, explaining 57.7% of the variability between studies. The global point prevalence of MDD, adjusting for methodological differences, was 4.7% (4.4–5.0%). The pooled annual incidence was 3.0% (2.4–3.8%), clearly at odds with the pooled prevalence estimates and the previously reported average duration of 30 weeks for an episode of MDD.
Conclusions Our findings provide a comprehensive and up-to-date profile of the prevalence of MDD globally. Region and study methodology influenced the prevalence of MDD. This needs to be considered in the GBD 2010 study and in investigations into the ecological determinants of MDD. Good-quality estimates from low-/middle-income countries were sparse. More accurate data on incidence are also required.
(Received March 08 2012)
(Revised June 05 2012)
(Accepted June 07 2012)
(Online publication July 25 2012)
c1 Address for correspondence: A. J. Ferrari, Policy and Evaluation Group, Queensland Centre for Mental Health Research, The Park Centre for Mental Health, Locked Bag 500, Sumner Park BC, Brisbane, QLD 4074, Australia. (Email: firstname.lastname@example.org)