I used to run a neurosurgical unit, but I've drawn a different conclusion. People assume that helmets save a lot of lives and even more brain damage - something must be better than nothing, right? - but actually the evidence seems to suggest otherwise. Counterintuitive, I know, but as more people have worn helmets we have not seen a commensurate decline in the number of head injuries per mile cycled. So while I have no objection to other people choosing to wear one, I am concerned that too many overestimate the protection a helmet can provide.

Not trying to start an argument here, there's a thread for that purpose in A&S. Just pointing out that knowing the consequences of head injuries doesn't necessarily equate to knowing what works in preventing them.