For nearly half a year, many people with attention deficit hyperactivity disorder have struggled to obtain their medication amid a nationwide shortage. The F.D.A. first announced the shortage in October, and Adderall is still in short supply. Among the patients who do manage to find Adderall, health care providers are left fielding their questions, though some say the concerns aren’t new. Danielle Stutzman, a psychiatric pharmacist at Children’s Hospital Colorado, estimates that up to a quarter of her patients over the past few years have said their medication seems less effective, a trend she said began around the start of the coronavirus pandemic.