Jennifer Lopez, Steven Tyler, Randy Jackson and host Ryan Seacrest told TV Guide Magazine that the Hollywood Week stage of the competition saw several contestants crumbling under the pressure of taking part in the competition.
Lopez said: "Last season, our Hollywood Week was easy breezy compared to this year, which was brutal. We had kids falling by the wayside...
"Kids were forgetting their words. Shaking in their voice. People we thought were going to be in the Top 10 were just crumbling. We were like, 'What is going on?' I guess it was the pressure of seeing the previous season and how it was big."
Tyler added that some contestants were "literally falling down", while Jackson elaborated: "Passing out, fainting."
Seacrest described this season's Hollywood Week as "physically intense for a lot of the contestants", although Jackson added that it was perhaps "even more intense" for the judges themselves.
The full interview appears in the new TV Guide Magazine, available January 5.
Executive producer Nigel Lythgoe recently said that there are no plans to introduce any major changes to season 11, saying: "I think we made a lot of tweaks last year. I'm not sure that we want to make too many more tweaks this year."
American Idol's tenth season was won by country singer Scotty McCreery in May, who went on to find success with debut album Clear As Day.
He was recently honoured with the 'Artist of the Year: New Artist' prize at the American Country Awards 2011.
McCreery recently said that he is looking forward to watching the new season more than any other in the past, saying: "I'll be watching those kids and know exactly what they're going through and the nerves they're feeling. It'll be fun to watch.
"I've watched for 10 seasons strong now, but it'll definitely be different to watch it this year."
American Idol returns with a two-hour premiere on Wednesday, January 18 on Fox.
Watch Scotty McCreery's music video for 'I Love You This Big' below: