Role of Patient Adherence in the Treatment and Prevention of Depression

Thesis (Ph.D.)--University of Washington, 2014Patient adherence to treatment and prevention guidelines as part of depression care is complex process. Major depression is a common disorder that can cause substantial morbidity, increase risks of mortality, negatively impact social relationships, and influence long term trajectories of education attainment and labor market outcome. Adherence is an important aspect of depression care because variability in compliance with prescribed treatments contributes to treatment effect heterogeneity and thus can decrease the effectiveness of viable treatments. This dissertation provides research to better understand barriers to pharmacotherapy and effects of patient adherence on health services use and health outcomes. Results from this project provide important information about characteristics of adherence and demonstrate the potential benefit allocating resources towards improving patient adherence for depression treatment and prevention. This dissertation examined determinants and consequences of adherence from different perspectives using observational data extracted from electronic medical records of a large integrated managed care maintenance organization as well as clinical trial data from a large multisite study. In the first aim of the dissertation, we studied the effects of industry-level unemployment on antidepressant pharmacotherapy using methods to control multiple channels of bias. We used medication persistence as our dependent variable, which measures the amount of time a patient accumulates medication from the beginning of therapy to discontinuation. We found empirical evidence that industry-level economic contraction interfered with optimal antidepressant therapy. In addition, we found the effect to be most pronounced during periods of economic shock and among mid-career employees. The second aim of this dissertation, we examined the effects of antidepressant adherence and persistence on medical care expenditures, also controlling for multiple sources of bias. We found a small but significant effect of antidepressant persistence on total costs excluding medications and on the costs of outpatient services. As persistence increased, our measures of medical care expenditures decreased. We conducted a longer-term economic evaluation of a clinical trial testing clinical- and cost-effectiveness of a depression prevention program and examined the effect of intervention dose on economic outcomes as part of the third and final aim of this dissertation. We demonstrated longer-term cost-effectiveness of the depression prevention program and showed higher doses of the intervention resulted in more favorable measures of cost-effectiveness. Our research signals the potential benefit of additional adherence promotion as part of an existing intervention program. Each aim in this dissertation project contributed policy-relevant research about barriers to patient adherence or about the effects of adherence on important patient outcomes. We applied rigorous quantitative methods to establish causality in our analyses, and applied these methods rich datasets from multiple sources. Our research findings provided meaningful contributions to the research literature in comparative effectiveness research, health economics, patient adherence, and mental health. In additional, we identified important areas of future research to be built on this dissertation project