the film's director david o russel is quoted as saying in an interview with dealdline.com
"You have to have those disturbing moments that let you know that the movie isn’t fooling around. And that the emotions are real, and that the people are real, and you want to be able to feel as much of that pain as you can in a real way. The movie is filled with heartbreaking moments, I think, and there’s some very painful ones when he bottoms out. You know, where Jennifer slaps him and what follows is this manic episode of anger and anguish with his parents. In romantic movies terms, it’s like she rang his bell but given his situation, it was a bell he wasn’t prepared for. He had all this baggage he wasn’t willing to let go of, and it became this catastrophe in the household. It was important to Bob and Jacki, but especially to Bob that we see this family moment. What I love most about that is how the family goes through this horrible trauma, and when the cop leaves, they’re just standing there, wiping their bloody noses and ears, in their pajamas, all traumatized, but you can already feel in the quietness of it, the love that’s knitting itself back together. It feels very poignant to me, like they’re in it together no matter what. They’re sticking together."
for the interview pertaining to Silver Linings Playbook start at 18:25