The 65-year-old opened up on his daily struggle with mental health in a cover interview for People magazine, explaining he's been experiencing symptoms of his OCD - repetitive and intrusive thoughts and fixations, often brought on by his debilitating fear of germs - since he was a child.
"I'm living in a nightmare," Mandel explains. "I try to anchor myself. I have a beautiful family and I love what I do. But at the same time, I can fall into a dark depression I can't get out of."
The former "Deal or No Deal" star, who has three children with his wife Terry, found the pandemic especially triggering for his mental health.
"There isn't a waking moment of my life when 'we could die' doesn't come into my psyche," he says. "But the solace I would get would be the fact that everybody around me was okay. It's good to latch onto okay. But (during the pandemic) the whole world was not okay. And it was absolute hell."
However, Mandel explained humour is a great way to get him through the darker moments of his conditions.
"If I'm not laughing, then I'm crying," he continues. "And I still haven't been that open about how dark and ugly it really gets."
"Comedy saved me in a way. I'm most comfortable onstage. And when I don't have anything to do, I turn inward - and that's not good."
The Canadian entertainer didn't go public about his conditions until 2006, and today still battles bouts of extreme depression, and a lack of understanding, something he hopes him being open will change.
"People see inconsistencies, especially in the media," he says. " 'Oh he hugged someone' or 'he shook someone's hand.' I can shake your hand. But then I'd think I didn't wash it well enough. And I'd go back and forth in a loop washing my hands for hours. I understand the funny in that. But it doesn't mean it isn't incredibly painful. And I don't want to defend my mental health. I just want to maintain it."