The source of the leaders’ relative serenity was pretty simple: control.

Compared with workers who toil in lower echelons of the American economy, the leaders studied by a group of Harvard University researchers enjoyed control over their schedules, their daily living circumstances, their financial security, their enterprises and their lives.

“Leaders possess a particular psychological resource — a sense of control — that may buffer against stress,” the research team reported Monday in Proceedings of the National Academies of Sciences.