Charlie Sheen's ex-wife Brooke Mueller is a "stage four" addict and "it's just a matter of time" until she relapses

She told PEOPLE: "When we're at stage four, it typically means that cycle where you just have these relapses, no matter how well you get, and no matter how many years, it's just a matter of time. I want to be honest about it, because if I try to sugarcoat it, I'd be lying to myself.

"The darkness and the shame as we get older, that sticks with us even more because we have more evidence of pain that we've caused others and ourselves.

"It's sad for us because we don't want this, nobody would want this. And so there's got to be a mental health component to it, where our suffering sometimes gets so strong that we literally - our brain tricks us and rationalizes why this time it's okay."

Brooke was married to 'Two and a Half Men' star Charlie from 2008 until 2011 and he's also been through addiction - so he always tries to help his ex whenever she's struggling.

She added: "He gets it. He's always there to help me and pick up the pieces ... But if I look back at our marriage, he was always one that could shut it off and turn it off and go to sleep, and I would be taking the car sneaking out to [Los Angeles area] Skid Row."

She went on to explain how her issues affect the twins, saying: "The sad reality, is they get used to it - Mommy is going to relapse again one day ...

"They've never tried a drink or drugs or been on a date yet. I can't tell you what I was doing at 15. They ended up being with their group of friends that happened to be really good kids."

Charlie previously opened up about his own spiral into addiction back in 2011 - which cost him his job on hit sitcom 'Two and a Half Men' - and led to bizarre public rants and he now looks back and can't believe he caused such "chaos".

During an appearance on the 'Loose Women' TV show, he said: "It feels awful. I can't sit there and lie to you. Some of it is very surreal. To this day, I am not sure how I created such chaos and wound up in that headspace. It's as though there was some alien or demonic possession going on."