Pretty terrifying 36 hours or so.

[Hell Hath No Fury]

7. Watch out for that concussion --

Please do some research on concussion and post concussion syndrome. It can take up to a few weeks for symptoms related to it show up, as well as several months for a possible TBI related depression. I don't say any of this to scare you, just for you to be aware of. I am 8 months post concussion and I am still experiencing significant symptoms. The next 2 weeks he should avoid over doing it on the computer, texting, watching movies or TV, doing mentally challenging processes like math. He is young and healthy, but a TBI at his age can cause issues now and even decades in the future.

http://www.brainline.org/

http://www.brainline.org/landing_pages/features/blkids.html