...but I don't think he's going to be a celebrity spokesperson for trichotillomania. For one- he doesn't even know what hair pulling is called. It's mentioned here in the first part of the interview with Jay Leno from October 15, 2012 (below).
And actually, I already knew that Ferrell had trich prior to this interview. I had googled "celebrity's with trich" once and his name came up. Supposedly he mentioned it in a GQ interview once, but for the life of me I could never find the actual article that said it. So I had only read things from others saying that he mentioned it once. So... here he is on Leno saying he was a hair puller. I doubt his interview will really help anyone, but... it doesn't hurt either. It's spreading a little more awareness.