Under-prescribing pain medications occurs during night shifts, according to a study published in Proceedings of the National Academy of Sciences. Shoham Choshen-Hillel, PhD, and colleagues explored time as a source of systematic bias in pain management in two studies. In the first, 67 resident physicians performed empathy for pain assessment tasks and simulated patient scenarios in laboratory conditions following a night shift or not. In the second study, this phenomenon was explored in medical decisions. Discharge notes from 13,482 patients with pain complaints were analyzed. In study one, physicians showed reduced empathy for pain following a night shift. In study two, physicians were less likely to prescribe an analgesic during night versus daytime shifts, and they prescribed fewer analgesics than recommended by WHO. After adjustment for patient, physician, type of complaint, and ED characteristics, this effect remained significant. For opioids, under-prescription for pain during night shifts was prominent.