I went back to work on reduced hours (and a one-to-one teaching setting instead of whole-class instruction) at 7 months post-concussion. The amitriptyline has helped a lot.
It's been a slow process of building up endurance to increased sensory input and just hours of being out of the house interacting with people.

Today I subbed for a whole-group class for one class period. It was still pretty overwhelming. I'm not sure how long it will take for me to be able to feel comfortable doing that for a whole day again.

But compared to being alone in my dim, quiet room all day like I was at the beginning of the summer, the fact that I was able to attempt an hour of regular teaching is pretty darn amazing!