"It was a really interesting creative process, writing with pretty much the biggest pop band on the planet," he told BBC Newsbeat backstage at the NME Awards.
The somewhat unlikely 'collabo' was first 'revealed' by One Direction frontman Niall Horan in January.
"It was a very different world and very different process — that was one of the reasons I wanted to do it. I really enjoyed it," Young continued.
"I felt like I took so much from doing it. I've always said I love pop music and how much I want to write pop music."
But do they contribute anything, Justin?
"It's the first time I've ever done anything like that. They do indeed contribute."