The 38-year-old, who has two-year-old daughter Aviana, also said juggling her career and motherhood left her so tired she could barely focus on the set, reported Contactmusic.
"I'd have to relieve the nanny after I got two hours of sleep, then go to work. There were moments when I was like 'This is the perfect movie to make on two hours of sleep'," she said.
Although the movie is based on a serious subject, Adams says she and her co-stars Philip Seymour Hoffman and Joaquin Phoenix had fun on set.
"Philip and Joaquin were a hoot. Although it's a serious subject, the experience was more fun than I expected," she added.