“Tully,” a movie about motherhood starring Charlize Theron that doesn’t open until Friday, is already generating a heated conversation about its portrayal of postpartum depression, a subject rarely depicted onscreen.

Now Diablo Cody, the writer of the film, has addressed the controversy for the first time.

“I don’t want anybody to think that I sat down and thought, ‘Oh, I’ll write a gripping and entertaining movie about something that I know nothing about,’” she said. “I would never presume to do that.”

Ann Smith, the president of Postpartum Support International, a nonprofit group, said her organization has been fielding complaints about the film since March, when spoilers began to circulate. (If you don’t want to know what happens in the movie, stop reading here.)

“The mommy world is up in arms,” she said, referring to survivors of perinatal mood disorders, which are diagnosed in one out of every seven women during pregnancy or postpartum. “I can see why there’s a lot of anger out there, and I think they have a right to it.”