Underwood: 'I need my personal space'

Carrie Underwood has revealed that she often suffered panic attacks while in high school.

The former American Idol winner said that large crowds, especially those encountered on occasions such as Christmas shopping, were her "worst nightmare".

"I'm a big personal space person. You know, if you go to the restroom, you use the stall that's not near anybody. Or if you're in the gym, you go to the treadmill where there's space in between you," she told Web MD magazine.

"And it seemed like in crowded situations like that, people would just completely violate your personal space. So, whenever I'd be in stores and there would be people touching me and kids running around, I couldn't take it and I'd have to leave."

Underwood added that the issue extended into her professional career and that it took a while to adjust to being close to her fans.

"They feel like they know you and they love you and that's wonderful – they're excited to meet you," she said.

"It just took me a minute to be able to figure that out and to be able to allow people into my space."