Several years ago, when Nicole Kidman was pregnant with her daughter, she began developing a big-screen adaptation of "Rabbit Hole," the Pulitzer Prize-winning play about parents suffering through the unimaginable loss of their young son.

The experience of bringing a life into the world while simultaneously shepherding a project about a life lost was an intensely affecting one for the actress, as she explained on Thursday at the film's red-carpet premiere. When production on "Rabbit Hole" began, daughter Sunday Rose was a year old, and Kidman found it difficult to let go of the characters at the end of each day.

"[It] deeply affects me," she told MTV News. "There were times when I woke in the middle of the night and I was having nightmares and I was really shaken by it. And that's when I know when something's really seeped into my subconscious and is disturbing me."

Co-star Aaron Eckhart — who plays Kidman's husband, one half of a couple being torn apart by the death of their child — similarly found himself reevaluating the idea of marriage and fatherhood. "It made me reflect on parenthood," he explained. "I'm not a father and I'm not married. Maybe someday I will be. I just put myself in that position of losing my son and almost losing my wife. I learned a lot about grief."

As dark as the material can be at times, the red carpet was anything but a depressing affair. Kidman was all smiles as she posed for pictures and answered questions alongside her husband, country music star Keith Urban. Jon Hamm, Parker Posey and co-star Sandra Oh were also on-hand for the celebration. Director John Cameron Mitchell pointed out that the festive mood was in keeping with the overall message of "Rabbit Hole," which opens in limited release on December 17.

"It isn't depressing," he said. "You are going to intense places, but everybody loves a good cry. Some people get that out in therapy, but many Americans do it through their entertainment. And this is an entertaining film despite its heaviness and it does end up with a lot of hope."

Check out everything we've got on "Rabbit Hole."

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