Harry Styles ''didn't realise'' Zayn Malik ''wasn't enjoying'' his time in One Direction.

The 'Pillowtalk' hitmaker quit One Direction in early 2015 after battling with anxiety, and his former band mate Harry has now admitted he and the other members - Niall Horan, Louis Tomlinson, and Liam Payne - were unaware of how much Zayn was struggling prior to his departure.

Harry, 25, said: ''It was kind of like we were sad, obviously, that someone had left, but also sad that he was not enjoying it so much that he had to leave. Because I think at the time too, the tour and everything was going so well and everyone had kind of got to this place where everyone was kind of living in a way where they I think felt pretty good. It felt like everyone was kind of enjoying it.

''I'd say a big part of it was us kind of being like, 'Wow.' You didn't realise he wasn't enjoying it that much.''

The 'Watermelon Sugar' singer says One Direction - who went on indefinite hiatus in late 2015 - became closer after Zayn's departure, because they had to rely on each other to overcome the ''hurdle'' of their friend's absence.

He added: ''We were about to start recording a new album and stuff and it was like, 'Are we recording this without him?' But I'd say in the moment, I guess the four of us became closer because we were like, 'OK, this is a hurdle that we weren't expecting.' ''

And although One Direction - who were formed on 'The X Factor' in 2010 - went on to release 2015 album 'Made In The AM' without Zayn, Harry insists the group began talking about splitting up as soon as Zayn left.

Speaking to Zane Lowe for 'New Music Daily' on Apple Music's Beats 1 Radio, the 'Lights Up' singer said: ''We'd sit down and have conversations [asking if] everyone [is] good, everyone wants to keep going and that kind of thing. There was a part of me where I felt like all of the decisions I'd made as an adult - that affected my life and what I was doing with my life - had been made as a group. I think there was a part of me that felt like I wanted to make some decisions for myself ... I felt like I needed to make some decisions that just affect me.''