The pan-European print group's supervisory board announced his decision to take early retirement this morning.
Explaining his rationale to PrintWeek, Caris said: "These are decisions you have to take sometimes in your life, and that's what I did. I told the board I would like to stop.
"It's something that's been growing for several months. It isn't about just one thing, it's about a complexity of items."
Caris has championed the case for industry consolidation across Europe, but has found his efforts stymied by both investors and regulators. Roto Smeets is currently in the midst of a protracted process that, if successful, will see the group taken private.
"I have mixed feelings. I am happy on one hand about my decision, but also sad because we didn't finalise what I thought was necessary and possible," Caris added.
Chairman Rudolf Huyzer and board member Bernard van der Heijden will take over Caris' duties while the bid by Printing Holding continues to go through due process.
Polestar chief executive Barry Hibbert said he was "saddened" at the news: "I'm sorry to see him go; he battles hard for the industry. John is an industry stalwart but also a nice man to do business with, and that's a rare combination these days."
Hibbert also described the current price war on the continent as "vicious". "How do you respond to 30%-40% price cuts? I wouldn't be surprised if we see a lot more casualties, both corporate and personnel."