Pop star Justin Bieber, who battled substance abuse as a teenager, says he used to take drugs to ease the pain because he was not satisfied with what he had achieved.

"There was a sense of still yearning for more. It was like I had all this success and it was still like: 'I'm still sad, and I'm still in pain. And I still have these unresolved issues.' And I thought all the success was going to make everything good. And so for me, the drugs were a numbing agent to just continue to get through," Bieber said in an interview with GQ Magazine, reports femalefirst.co.uk.

However, he says he soon realised this was not who he wanted to be.

"And then you're this young angry person who had these big dreams, and then the world just jades you and makes you into this person that you don't want to be. And then you wake up one day and your relationships are f***** up and you're unhappy and you have all this success in the world, but you're just like: Well, what is this worth if I'm still feeling empty inside?" he said.

This is when he turned to God, he said.

"He is grace. I came to a place where I just was like, 'God, if you're real, I need you to help me, because I can't do this on my own. Like, I'm struggling so hard. Every decision I make is out of my own selfish ego," he said.