Why is major depression prevalence not changing

Abstract Background Increasing provision of treatment should theoretically lead to a decreased burden of major depressive episodes (MDE) in the population. However, there is no evidence yet that this has occurred. Among possible explanations are that: (1) treatment may not be sufficiently accessible, effective or effectively delivered to make a difference at the population level or (2) treatment benefits such as diminished episode duration may be offset by other trends such as increasing episode incidence, or vice versa. Methods MDE prevalence has been assessed in a series of national surveys and in a single national longitudinal study in Canada. These studies included a short form version of the Composite International Diagnostic Interview module for major depression. Indicators of incidence and episode duration of MDE were estimated. Meta-regression methods were used to examine trends over time. Results No evidence of increasing incidence nor of diminishing duration of MDE was found. The analysis failed to uncover evidence that the epidemiology of this condition has been changing. Limitations Most studies included in this analysis used an abbreviated interview for MDE which may lack sensitivity and/or specificity. These studies could not address potential benefits of treatment on prevention of suicide. Some potentially offsetting effects could not be assessed, e.g. economic or societal changes. Conclusion These results suggest that more effective efforts to prevent MDE, or to improve the volume or quality of treatment, are necessary to reduced burden of MDE in the population.