Hemingway is the granddaughter of the literary great Ernest Hemingway, who committed suicide several months before she was born. In the documentary, the 51-year-old actress talks about the pain of growing up as a Hemingway and the string of suicides in her family.
The actress also recalls how "crazy" life at home was, considering both her parents drank and fought frequently.
"I didn't feel like I was crazy, but I felt like I lived in crazy. You know, in the land of crazy," she says.
"[My parents] would have one glass of wine and things were kind of happy," she recalls. "They were actually having a regular conversation. But after a couple glasses of wine, the alcohol kicked in. Nastiness would happen."
The film also mentions Hemingway's oldest sister Margaux, once a supermodel, who overdosed and died at age 41, and how her eldest sister Muffet remains under psychiatric care after suffering a series of psychotic breaks.
Asked if she's worried about her own mental health, Hemingway says that right now, she's fine.
"You know what? I can honestly tell you for the first time in my life, the last four years, I do not think that some secret, dark night's gonna come and, like, pounce on me, which I used to. For many, many years I thought, it's my turn," she explained.
As for her new love Bobby Williams, Hemingway says he was the one who taught her how to laugh. She added that "pretty much all of her happiness" comes from being with him.
In the end, Hemingway admits that she has finally found herself.
"There's that quote that it's never too late to have a happy childhood," Mariel said. "It's really true. If you want to, you can recreate a life that is right for you. And that's what I've done."
Running From Crazy opens in theaters in select cities beginning November 1.
Notable deaths of 2014 [PHOTOS]