Not just that. Younger children feel parent's stress, in real time as it happens more intense than older children. Everybody remembers being a kid and having that awful feeling in the gut when their mother or father was upset, angry or stressed. The god awful feeling. Well, babies have that as well only much more intense than 6 year old, or 9, or 12 year old or a teenager. But it's the exact same thing. I think this alone in excess amount can add up to trauma at very young age. If child feels that way more hours of the day than not, every single day that's fucked up. And inevitably forgotten.