Several celebrity guests turned out for the final new “Saturday Night Live” broadcast of 2018, including Alec Baldwin, Ben Stiller, Matt Damon and Robert De Niro. But the show featured only the briefest of appearances from the cast member Pete Davidson, who on Saturday afternoon published an Instagram post that elicited widespread concern about his safety and well-being.

The post from Davidson said: “I don’t really want to be on this earth anymore. I’m doing my best to stay here for you but I actually don’t know how much longer I can last. All I’ve ever tried to do was help people. Just remember I told you so [heart emoji].” His Instagram account was deactivated shortly after it was published.

The New York Police Department said on Saturday afternoon that it had sent an officer to NBC’s Manhattan headquarters to check on Davidson, 25, who has spoken publicly, on “S.N.L.” and elsewhere, about being given a diagnosis of borderline personality disorder and his efforts to improve his mental health.

Davidson did not participate in any of the live comedy sketches on this weekend’s episode, which was hosted by Damon. But Davidson did appear around 12:50 a.m. to introduce a musical performance by Miley Cyrus, Mark Ronson and Sean Ono Lennon. Davidson was also shown in a pretaped segment satirizing the efforts to find a host for the Academy Awards.