Objective: Multiple Sclerosis (MS) is associated with elevated levels of depressive symptoms and an elevated frequency of depressive disorders. Depressive disorders, in general, are associated with substantial direct and indirect economic costs, and have been shown to increase the costs associated with the management of medical conditions in a variety of clinical settings. However, the impact of depressive disorders on costs associated with MS have not been evaluated. The objective of this study was to evaluate this association.
Methods: The Composite International Diagnostic Interview (CIDI) was used to identify subjects with major depressive disorder in a sample who had earlier been selected for a broader economic evaluation of the costs associated with MS. Costs were measured in two ways: retrospectively (by questionnaire covering a 2-year period) and prospectively (using a 6-month diary). The proportion of subjects reporting any costs and the proportion exceeding various cost thresholds were calculated in subjects with and without lifetime major depression. These proportions were compared using exact statistical tests and confidence intervals. Non-parametric (rank sum) tests were used to compare median costs.
Results: Of 136 subjects, 31 had a lifetime history of major depression. MS-related expenses evaluated retrospectively (e.g., house and vehicle alterations and purchases) did not differ depending on major depression status. In the prospective analysis, subjects with lifetime major depression were more likely to purchase vitamins, herbs, and naturopathic remedies (p < 0.01) and more likely to incur costs associated with utilization of services provided by alternative practitioners (p = 0.04). Other differences (e.g., in mental health care, medical specialists, general practitioner visits) were not observed.
Conclusions: Contrary to expectation, this study did not find increased direct medical costs in persons with comorbid major depressive disorder and multiple sclerosis. Persons with comorbid MS and (lifetime) major depression did not incur greater costs or utilize more services. The Canadian health care system is guided by principles of universality and is publicly funded and administered, however, the lack of an impact of major depression on utilization may reflect limited access to services. The lack of an association between costs and major depression may or may not be generalizable to health care systems in other countries.