Keane frontman Tom Chaplin has returned to the stage following his treatment for alcohol and drug addiction.
Keane's last performance was at the V Festival in August
He told the audience in Hull on Tuesday that the gig felt like "a big group therapy session".
In a BBC Radio 1 interview, Chaplin said that says his life had become "unmanageable" when he entered rehab.
"You walk to the edge of the cliff and look into the abyss, and either kind of jump off or turn around," he said. "Thankfully, it was the latter."
The concert was in stark contrast to the band's last appearance at the V Festival in August, when the singer looked pale and drawn.
He checked into rehab the following day.
"I wasn't happy and I wasn't enjoying myself," the 27-year-old singer told Radio 1 of his decision to enter the Priory.
"When your life becomes unmanageable that's when you have to do something about it."
The singer stressed that the clinic, which has treated many famous people including Pete Doherty, Caroline Aherne and Justin Hawkins, was not a "trendy health farm".
"There are people in there, including myself, who do have a lot of problems. People who are dealing with life and death situations."
Chaplin left the clinic two weeks ago and said he was "taking it as it comes".
Keane, which also features drummer Richard Hughes and keyboard player Tim Rice-Oxley, won two Brit Awards last year for best British album, for their debut Hopes and Fears, and best British breakthrough act.
Two years ago, they topped the BBC News website's Sound of 2004 poll of UK critics and broadcasters, which focuses on up-and-coming acts.
Their follow-up album, Under the Iron Sea, entered the UK chart at number one in June.