Changes in opioid prescribing in veterans with headache during the COVID-19 pandemic: A regression discontinuity in time analysis. - Wang K; Fenton BT; Skanderson M; Black AC; Becker WC; Seng EK; Anthony SE; Guirguis AB; Altalib HH; Kimber A; Lorenze N; Scholten JD; et al. (Headache, 2023)