Global Burden of Disease 2017 estimates for Major Depressive Disorder: a critical appraisal of the epidemiological evidence.

Objectives: To critically appraise the quality of the studies underpinning the Global Burden of Disease (GBD) 2017 estimates for Major Depressive Disorder (MDD) with respect to i) the GBD 2017 inclusion criteria and ii) population coverage.

Design: Systematic critical appraisal.

Setting: Not applicable.

Participants: Not applicable.

Main outcome measures: Each study was critically appraised with respect to the four GBD 2017 inclusion criteria: representativeness, study method and sample, diagnostic criteria and publication from 1980 onwards. Population coverage was calculated.

Results: Less than half of studies (221/467, 47.3%) were nationally representative. Only 262/467 (56.1%) of studies reported specifically on MDD and more than a third did not use DSM or ICD diagnostic criteria: 94/467 (20.1%) did not specify any diagnostic criteria and 68/467 (14.6%) relied on self-reported depression for diagnosis. Only 62/467 (13.3%) of studies were conducted during the period 2011-2017. Only 107/195 (54.9%) of countries had one or more prevalence studies.

Conclusions: GBD 2017 estimates for MDD are based on incomplete country and population coverage. The inclusion of studies with non-representative populations, that do not use diagnostic criteria and the lack of specific data on MDD reduces the reliability of estimates and limits their value for policy making.