Country superstar Carrie Underwood's early career was blighted by panic attacks as she struggled to cope with her overnight success.

The Before He Cheats hitmaker became a household name in the U.S. after winning the fourth season of American Idol in 2005 and has gone on to release four best-selling albums.

She admits her success came at a price as she fought severe anxiety issues due to the huge amount of interest in her life at the beginning of her music career.

Underwood tells Marie Claire magazine, "At the beginning of my career, I used to have panic attacks. People were touching me, screaming - it made me really nervous. In public, I just get nervous. It's a physical reaction, feeling like the walls are closing in.

"The fans are great. It's not their fault. I don't ever want to come across as ungrateful. But on my end, it is hard for me to process. Because I am still just me."