Nicole Kidman is "so attached" to her children she wakes up at 3am panicking about them when they are apart.

The actress has adopted kids Connor and Isabella with her ex-husband Tom Cruise and raises daughters Sunday Rose and Faith Margaret with her spouse Keith Urban.

Her job means she is often away from her loves ones, which the 45-year-old still finds hard.

"I'd love to say that it's easy, but it isn't. I miss them so much when I'm away. And so I limit the amount of time away through no other reason than I just love, I love them. But that's my personality. I get 3am panics because I'm so attached," she told the November issue of Harper's Bazaar.

Isabella is 19 and Connor is 17, and Nicole can't believe two of her children have grown up. She's amazed by how quickly time has passed and is enjoying every minute of raising her younger daughters.

Being with Keith has also grounded her. "He just gave me confidence through just being very kind to me and understanding me, opening me up to trying things, my sexuality, those sorts of things," she said.

"[He is] more like an ocean; he took me out. [I've always appreciated] a bigger, stronger personality; that's what I've been drawn to. I need protection. Everyone wants to feel someone's got their back."