Researchers estimate that between 4.5 million and 15 million children are exposed to physical violence in the home. Verbal and emotional abuse in the home is more difficult to track.

Social workers, health care providers and academics have long tracked the effects of trauma suffered by children growing up in urban neighborhoods with frequent gunfire and other violence. But outside of medical journals, there has been little reporting on the effect of the more common domestic violence on the millions of children who grow up on the residential battlefields where it occurs.

Neuroscientist Tanja Jovanovic directs the Grady Trauma Project, a research institute based at Emory University in Atlanta. The risk of PTSD from domestic violence is high, she says, because it's a "betrayal by someone who is supposed to be to a protector."

Making matters worse, Jovanovic said, domestic violence often eliminates the "buffering effect of another positive adult," because the adult who is targeted can't provide comfort to the children who witness it.

Psychologist Abigail Gewirtz says domestic violence can feel scarier than war. Gewirtz is the director of the Institute of Translational Research in Children's Mental Health at the University of Minnesota. It's "one of the most terrifying forms of violence because it happens in a place which is supposed to be safe," she said. "Children are totally powerless, especially very young children. They are totally dependent on their parents.”