These are not only the best of times and the worst of times. They also are nerve-wracking, nail-biting times for tens of millions of Americans: Slightly less than a quarter of adults and a rising number of young people suffer from anxiety disorders, which have become the nation’s most common and pervasive mental woes.

They’re as real to those who suffer from them as any physical complaint. The deep apprehension that sufferers feel exceeds the worry or jitters that are part of everyday life. Rather, it becomes a dread that patients and experts describe as “deep, persistent, seemingly uncontrollable, overwhelming, excessive, irrational, and disabling.” It’s often accompanied by crushing depression...