The singer revealed that she once ended up in a coma, which has put her off taking drugs in the future.
"I experimented with drugs and I ended up in a coma after taking too much.
"But I had a horrendous experience before falling into a coma," she told The Sun. I was getting flashbacks and that created an anxiety disorder. I got diagnosed with PTSD.
"I was incredibly lucky. I could have died, but I woke up. Now I'm terrified of drugs and I'd never touch them again."
Bruce explained that her turbulent relationship with her father was one of the main reasons for her past drug use.
"I've never put a reason on why I ended up in a dark place but experimenting with drugs and the relationship with my dad didn't help.
"I haven't spoken to him for a long time and I hope it stays that way."
Bruce also spoke of her previous "s**tty" jobs while trying to crack the mainstream.
"I've been trying to get a break for such a long time and kept getting doors slammed in my face," she said.
"I lived in New York for a while sleeping on people's floors but nothing worked out.
"I even worked as a receptionist at Warner Brothers in London - I did all sorts of s**tty jobs."
The singer's fellow finalist Tyler James has also spoken about his past drug use before entering the show, and how it also once put him into a coma.
Bo Bruce will face off against Leanne Mitchell (Team Tom Jones), Vince Kidd (Team Jessie J) and Tyler James (Team Danny O'Donoghue) in the live final.
The finalists will compete in the final on Saturday, June 3 at 7.20pm on BBC One.