The Rosie Webster actress, who stood down from her Weatherfield role last October, explained that she felt "trapped" on the show she had been part of for 11 years.
Flanagan, who has relocated to Australia to compete on this year's I'm a Celebrity...Get Me Out of Here!, is quoted as saying in this week's Reveal magazine: "I've suffered from depression.
"It was the main reason I had to leave Coronation Street. I was down and it was very intense - I don't think I was very well.
"I wasn't happy there any more. I wanted to find my own identity and I didn't feel free - I couldn't be myself or do what I wanted to do.
"I like to think I'm strong, but I really struggled. My head was in such a state that I wanted to run away, without thinking where I'd go or how I'd get there."
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Copyright: ITVThe star continued: "I felt trapped. It wasn't just work, I felt overwhelmed in general. People will think I'm an ungrateful cow.
"Like, what's so bad about my life that made me depressed? I have a good job, money, this and that."
Flanagan suffered a series of panic attacks shortly before announcing her Corrie exit.