JoJo drank alcohol to help her "get out of her mind".
The 'Too Little Too Late' hitmaker has had "many low points" in her life including being told she had to lose weight or she wouldn't have an album released by a former record label.
She said: "I've had many low points, honestly. I thought, 'How can I come back from this, you know, too much time has passed.'
"I was depressed, I was drinking a lot because I wanted to get out of my mind. I'm being totally honest ... I just wanted to feel good and get out of my mind and that was obviously trying to fill a hole that I had."
And the 25-year-old singer admits she has lost her confidence partly because of what has happened in the past.
She told Entertainment Tonight: "I don't feel confident one thousand per cent of the time, but oftentimes I write the songs that I need to hear, with the messages that I need to.
"I feel like, particularly as females, sometimes we apologise for taking up space ... for taking the moves that we need to make, whether we realise that we're being apologetic for it. So, it really is just about knowing who you are, digging who you are, not making excuses to make other people feel comfortable."
Meanwhile, JoJo previously opened up about her battle with her former record label.
She shared: "Here's something that I agreed to do that ended up messing with me psychologically. I was under a lot of pressure with a company I was at previously and they wanted me to lose weight fast.
"So they got me with a nutritionist and had me, like, on all these supplements, and I was injecting myself - this is a common thing 'the girls' do all the way - it makes your body only need certain calories, so I ate 500 calories a day. It was the most unhealthy thing I've ever done. I felt like, 'If I don't do this, my album won't come out.' Which it didn't! So it's not like it even worked!"
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