The Lead Balloon star told Closer magazine it was about time he opened up about his mental health.
Jack, who has spent much of his life battling depression, said: "I don't know why comedians are such a miserable bunch. Maybe it's what makes us comedians.
"I've had times where I've felt very, very low and it's not nice. You learn coping strategies, and I find that keeping busy can be very helpful."
Jack has also been described as a recovering alcoholic in the past, but he insisted he can now enjoy a drink and said there was just a phase where his boozing was out of control.
"I was probably using alcohol to counteract my depression and that's really not a good idea," he said.
"I don't talk about my depression very much, but I can't deny it. And let's face it, bipolar seems to be the new rock 'n' roll, doesn't it?"
:: The full interview is in Closer magazine, out tomorrow (Tuesday).