'Some Hope Is Better Than Having No Hope'

When the F.D.A. approved the drug Aduhelm, the first Alzheimer’s treatment to receive the agency’s endorsement in almost two decades, it gave hope to many. But the decision was contentious; some experts say there’s not enough evidence that the treatment can address cognitive symptoms. What is the story behind this new drug? Guest: Pam Belluck, a health and science writer for The New York Times.