Actor Will Smith says his children -- Trey, Jaden and Willow -- have stopped taking advice from their parents `a long time ago` as they are grown ups now.

"You know, listen, I have a 23-year-old, a 17-year-old, and a 15-year-old, so they were done listening to me a long time ago," Smith told usmagazine.com.

Smith's latest film `The Concussion` sees him star as Dr. Bennet Omalu, a pathologist who makes history when he uncovers the link between permanent brain damage and the frequent head injuries professional footballers suffer from.

Shooting the film, which is based on a true story, made Smith even more aware of the dangers of the sport, and he says watching the finished movie as a parent was a harrowing experience.

"It was a little scary because my son played football for four years and it (brain injuries) was never even was a subject. It never came up. We were concerned about him breaking his leg, or spinal injury was the big thing that all of the parents were concerned about," Smith said.

`So it was scary to me -- it was almost as if it was hidden in plain sight. And as I started to understand the science, I knew that it was something that I wanted to deliver to the world," he added.