Medicine: Is Mental Illness Inherited?

It is rare to find a chatterbox among the Amish of Lancaster County, Pa. Rarer still is a flamboyant personality, a braggart, a show-off or, at the other extreme, someone who is deeply depressed or suicidal. In this community of quiet-spoken, humble pacifists, such behavior "really stands out against the social landscape," observes Medical Sociologist Janice Egeland, who has spent more than 25 years among the Old Order Amish, as the group is formally known. When it does occur, the Amish often have an explanation: "Siss im blut," they say; the peculiar behavior is "in the blood."

Last week Egeland, who...