The Effects of an Emergency Department Opioid Prescription on Long-Term Outcomes (with Sarah Eichmeyer) **PLEASE NOTE EARLIER TIME**

In the past two decades, death rates from opioids have seen a five-fold increase and opioid prescribing has emerged as a leading public health problem in the United States. In this paper, we study the extent to which a single opioid prescription in emergency departments can induce long-term dependence and impact health and economic outcomes of patients. We tackle these questions by leveraging quasi-random assignment of patients to physicians, who vary in their propensity to prescribe opioids. We analyze the universe of electronic health record data for a particularly vulnerable population - veterans - and find that a single opioid prescription induces a 1.2 percentage point (pp) increase in the probability of long-term opioid use, a 0.07pp increase in recorded opioid overdose, and a 0.075pp increase in death from an opioid overdose. We find suggestive evidence of transition into illicit opioids. Moreover, in settings where the supply of legal prescription opioids is restricted, veterans are more likely to resort to illicit opioids, highlighting the complex inter-dependencies between legal and illicit sources of opioid supply.