The Impact of Cost Sharing on Antidepressant Use Among Older Adults in British Columbia

Abstract

Objective-Antidepressant therapies are underused among older adults and could be further curtailed by patient cost-sharing requirements.The authors studied the effects of two sequential costsharing policies in a large, stable population of all British Columbia seniors: change from full prescription coverage to $10-$25 copayments (copay) in January 2002 and replacement with incomebased deductibles and 25% coinsurance in May 2003.Methods-PharmaNet data were used to calculate monthly dispensing of antidepressants (in imipramine-equivalent milligrams) among all British Columbia residents age 65 and older beginning January 1997 through December 2005.Monthly rates of starting and stopping antidepressants were calculated.Population-level patterns over time were plotted, and the effects of implementing costsharing policies on antidepressant use, initiation, and stopping were examined in segmented linear regression models.Results-Implementation of the copay policy was not associated with significant changes in level of antidepressant dispensing or the rate of dispensing growth.Subsequent implementation of the income-based deductible policy also did not lead to a significant change in dispensing level but led to a significant (p=.02) decrease in the rate of growth of antidepressant dispensing.The copay policy was associated with a significant (p=.01) drop in the frequency of antidepressant initiation among persons with depression.Income-based deductibles reduced the rate of increase in antidepressant