I've had about 5 documented concussions from basketball and bike riding, probably quite a few more minor ones as well. It comes down to risk/reward. Yes concussions can cause serious longterm damage but I don't want to sit on my couch all day and be scared of doing anything where I could get a concussion. Just be smart about it and wear a helmet. What good is having a great memory when you're 80 if you have no fun memories?