The 'Black Parade' rockers split in March 2013, and the frontman admits he knew it was time to call it a day because the band was making him ill and affecting his personal life.
He said: ''It was one of those things that actually was painful and slow, a sequence of breaks. But it comes down to me just being really depressed.
''It's hard to go into too much detail about the mechanics of it, but one day I just said, 'You know, we can't do this.' It was really hard. Nobody was happy. I wasn't happy.
''I felt like I was in this thing that I couldn't get out of, because I was partially responsible for other people's lives. And then it started to make me physically sick, and it started to affect my personal life.''
Gerard feels he has been able to move forward since leaving the band, and though he didn't plan a solo career, he has been working hard on a new album.
He told NME magazine: ''Being in a band holds you in stasis. There's a refusal to grow past a certain point and I personally stopped growing.
''I guess I thought I was going to have a 'normal' life after My Chemical Romance, but then all of a sudden I started to plan out what a solo career would be like.
The first single from Interpol's eagerly anticipated sixth studio album 'The Rover' has dropped alongside a video.
'Jumpsuit' is just one of two singles, including 'Nico and the Niners', released ahead of Twenty One Pilots' latest album 'Trench'.
They unveiled a new video showing the making of the record.