Justin Bieber
Justin Bieber's mother, Pattie Mallette, has written a book about her tumultuous life. Reuters

Teen pop sensation and heartthrob Justin Bieber has revealed that he was bullied as a child.

Bieber has taken a step ahead to stand up against bullying by lending his song 'Born To be Somebody' to The Weinstein Company's documentary entitled 'Bully'- that talks about bullying in school.

"I was bullied," he said on the show Showbiz Tonight.

"Most people in their lifetime have been bullied at some point. I think that it's about time that people start making a change. I think a lot of times principals just let it go, teachers let it go and other students just let it go, but I think this movie is really powerful and can help change a lot of lives."

The 18-year-old singer said that he understand the subject in its real sense as he suffered at the hands of bullies while at school.

"Just watched the #BULLY movie. really intense. really powerful. we need to stand up for each other," Bieber tweeted.

The documentary "Bully'', directed by Lee Hirsch, looks at the issue of school bullying through the eyes of five youngsters who have been the victims of bullying. It could be at school, online or on the school bus, and some way we all are affected by it.

Earlier the MPAA restricted the access of the movie to the age group, who are most affected by the film's subject, by rating it an R. The decision was taken due to the depiction of real-life language used by the bullies.

But following the campaign with the support of high- profile celebrities including Bieber to change the rating, MPAA approved "Bully" a PG-13 rating after a few instances of swear words were edited.

"The small amount of language in the film that's responsible for the R rating is there because it's real," Hirsch said in a statement. "It's what the children who are victims of bullying face on most days. All of our supporters see that, and we're grateful for the support we've received across the board. I know the kids will come, so it's up to the theatres to let them in."

Bieber urges those who witness bullying or who experience it to speak up to stop bullies to watch the film. "If you're a bystander, too, tell somebody - because a lot of times, it's just not spoken of, and you ended up - you end up keeping it all inside, and then it just hurts even more."

He also hopes his fans will support the film's message."My fans are always up for supporting a great cause. It's one of the things I'm most proud of as an entertainer," he says in the statement. "I hope they see "Bully" with their friends and help start the conversation so we can end bullying."

Other than pop star Justin Bieber, the other celebrities who have thrown their support behind the film are Johnny Depp, Ellen DeGeneres, Meryl Streep, Kelly Ripa and Anderson Cooper.

"Bully" is all set to open nationwide on April 13.