My kids have had between them 3 diagnosed concussions and 1 suspected. I have spent too much time at the St. Charles concussion clinic. They told me that helmets do NOTHING toward preventing concussion. All helmets do is protect against skull fractures and lacerations.
Concussion is caused by the brain rattling around inside the skull. As such, you can see that a helmet is not going to alleviate that motion at all. Concussions happen often when one's head is whiplashed, not from a blow.
| 
