I’ve had concussions and never been told to abstain from screens. So, I did some quick googling... by the looks of it, screens (and other bright light sources) can exacerbate post-concussion headaches, but I didn’t see anything that indicated screen use slows recovery or causes further damage.
The understanding I've gotten from reading about the topic and talking to a GP was that anything that makes symptoms worse will lengthen recovery time.
