Pete Davidson made a brief appearance on 'Saturday Night Live' (15.12.18), hours after he sparked concerns about his mental health with a worrying Instagram post.

Pete Davidson

Pete Davidson

The 25-year-old comedian - who suffers from bipolar disorder and has previously battled suicidal thoughts - was the subject of a welfare check by the New York Police Department (NYPD), earlier in the day after he wrote on social media that he "doesn't want to be on this earth any more".

However, he appeared on 'SNL' briefly on Saturday when he introduced Miley Cyrus, Mark Ronson, and Sean Ono Lennon to sing John Lennon's 'Happy Christmas (War Is Over)'.

Pete's pre-taped sketch about potential new Oscars hosts also aired.

Earlier, Pete had sparked concerns among friends, fans and his former fiancée Ariana Grande when he made his worrying Instagram post just moments after he praised Kanye West for speaking out about his own mental health struggle after Ariana made a joke concerning Kanye's online feud with Drake.

Pete wrote on Instagram: "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."

The star only left the post up for a matter of minutes before he deleted his entire Instagram account.

Ariana later took to Twitter to share her own worries, and confirmed she has rushed to Pete's side to support him.

She tweeted: "man i'm so sorry i told a dumb joke. i really didn't mean any harm. all i want everyone to be healthy and happy. so desperately. please. my god.

"I'm downstairs and I'm not going anywhere if you need anyone or anything. I know u have everyone u need and that's not me, but i'm here too. (sic)"

Several stars also took social media to offer messages of support to Pete.

Jada Pinkett Smith wrote: "Pete Davidson ... hang in there. There is a lot of help out here. Surrender to some love some where around you ... today! Right now! And then ... let in the help that will become available. I'm praying for you Pete. I've been there. It gets better. (sic)"

And Nicki Minaj tweeted: "We can be so insensitive. God bless Kanye & Pete. Being flippant about mental illness speaks more about you than them. Stop saying the word love & live it. Love is an action. (sic)"