This is Fusco et al. (2023). The authors review the literature on studies published between 2010 – 2020. They find that there are 79 articles:
There was no difference in the type of disease, but most publications found that higher cost-sharing was associated to poorer adherence, persistence, and discontinuation. According to the aggregate data, higher cost-sharing was associated with worse adherence. One study found that cost-sharing was associated to worse clinical outcomes. Three other studies did not find significant differences. Concerning HRU [healthcare resource utilization]Higher-cost-sharing tends to lead to decreased outpatient utilization and greater inpatient use. All evidence suggests that higher cost sharing has a neutral to negative overall impact on total expenses. The impact of eliminating copays on total costs was either reduced or eliminated in studies that examined the issue.
The paper faces two challenges: i) publication bias, and ii) cost sharing measurements. Is it possible that papers without a relationship between cost sharing, adherence, cost, and cost are less likely to get published? Potentially….