2025

Ahomäki, Iiro

This doctoral dissertation studies empirically the effects of information interventions on physician prescribing behavior. The dissertation consists of an introductory chapter and three articles. The first article studies how a physician-targeted information letter, aiming to draw physicians’ attention to their prescribing practices of paracetamol-codeine combinations affects opioid prescribing. Using individual-level register data on filled prescriptions and a difference-in-differences strategy, we estimated that the letter decreased the average number of tablets purchased by new patients by roughly 13% and the probability of a first purchase being at least 100 tablets by 6 percentage points. The effects were larger for consistent high prescribers. The second article examines the impacts of an information intervention on physicians’ prescribing practices of tricyclic antidepressants and pregabalin, and patients’ healthcare utilization. National guidelines identify these drugs as potentially inappropriate for older adults. We use a research design based on difference-in-differences design and nationwide register data on filled prescriptions and health care contacts. We found that the intervention decreased the probability of prescribing tricyclic antidepressants and pregabalin to patients aged 75 or older by 29%. The filled quantity of these drugs was reduced by 12%. No effect on patients’ healthcare utilization was detected. The third article studies the impact of an information intervention on strong opioid prescribing. The article used a preregistered randomized research design and nationwide data on prescriptions. The intervention showed no significant effects in the whole study population, but we detected heterogeneity in effect with respect to preregistered physician characteristics. We observed a 22% reduction in fentanyl and oxycodone prescriptions to new patients among physicians receiving their first information letter, a 5% reduction in any opioid prescriptions among high-volume prescribers as well as an increase of 7% in nonopioid analgesic prescribing among low-volume prescribers. Information interventions can be an effective policy tool when the aim of the authority is to get physicians to prescribe less of particular drugs. The interventions are less likely to be effective when the targeted physician population has previously received similar interventions.