Executive Summary
After rising for more than 40 years, the number of U.S. drug overdose deaths began to fall in mid-2023, declining from a 12-month rate of about 110,000 in June 2023 to about 72,000 in August 2025, primarily as a result of a decline in the number of deaths involving fentanyl. Many factors have been suggested to explain that unanticipated decline: some focused on supply and some on people who use illicit drugs, including widespread adoption of several harm reduction measures. This essay examines five different potential sources of decline. Two are specific policy interventions aimed at reducing demand or mortality risk; for neither intervention do we assess the effects as likely to be substantial. Two sources are characteristics of the supply that may have changed to reduce mortality; both may have played a role. The fifth is purely epidemiological, and we are unable to assess its impact. The brief concludes with recommendations for strengthening monitoring systems to improve policy.