It used to have a different euphemism. If a star needed a break from a project because of a drinking problem or an eating disorder or just an old-fashioned psychological meltdown, a press agent would release a statement blaming the sudden hiatus on "exhaustion." 

As PR baloney goes, it was a gorgeous lie, suggesting that the actor or actress in question was the victim of too crushing a work ethic and simply needed a breather from their own relentless perfectionism. Chef's kiss to whoever came up with it.

Today, though, performers are apparently inexhaustible. They still unexpectedly bolt from the public stage — in fact, in recent months a shocking number of them have been dashing off for unscheduled respites — but nowadays that vanishing act goes by a different name. It's called a "mental health" break.