Why is Major Depression Prevalence Not Changing?

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.