Oh, and NO, it isn't safe to smoke with a concussion. Anytime your brain is healing, besides getting bonked on the head again, the worst thing could be to fill up your head with chemicals that either change the healing process or slow it down.
I highly suggest anybody that wants to smoke during a concussion or that might have had two concussions within a small time period read this. It's about a friend of mine and it's a powerful article:
http://www.burlingtonfreepress.com/apps/pbcs.dll/article?AID=/20060618/NEWS01/606180309/1009&theme=