Objective: The prevalence of major depression is increased in people with chronic medical conditions. The objective of this analysis was to determine whether this is due to a higher incidence, an impact on prognosis, or an effect of mortality.
Study design and setting: An analysis of data collected in two national Canadian general health surveys was carried out. Markov models representing period prevalence, incidence, mortality, and recovery were developed using these data sources. Monte Carlo simulation, using tracking variables, was used to evaluate the model.
Results: The incidence of major depression was higher in subjects with chronic medical conditions. However, the pattern of recovery was also different: Subjects with chronic medical conditions had slightly longer episode durations. The analysis of mortality data was limited by a small number of deaths in the survey sample; however, the models suggested that the impact of mortality on the association is small.
Conclusion: An elevated prevalence of major depression has been observed in persons with chronic medical conditions. Two factors seem to contribute to this association: increased episode incidence and duration.