A man receives a dose of the Johnson & Johnson coronavirus vaccine on April 23. (Jorge Guerrero/AFP/Getty Images)

When the Centers for Disease Control and Prevention added mood disorders to the list of conditions that put people at high risk for severe coronavirus cases recently, clinicians were not surprised. The mind-body connection, they say, is long-settled research.

But the scientific seal of approval is still critical: It makes millions of people eligible for booster shots based on their mental health diagnosis alone and gives vulnerable groups more reason to protect themselves.