We’re pretty sure most people would agree that all things equal, you are better off wearing a helmet than not, if you happen to be in an accident. Hell, even if tying a rubber chicken to you head increased your survivability by 1%, you’d be crazy not to tie one on if you knew you would be coming off your bike.
But dangerous? How could that be possible?
Of course there is some evidence that helmets cause some types of neck and brain injuries by increasing the rotational forces on the head & neck; this serious brain injury type is known as diffuse axonal injury (DAI). Granting that the DAI thesis is true for a moment, the real question is whether the improved protection from linear deceleration outweighs the possibility of a DAI from rotational forces – something we are not sure about (if you have any evidence to the contrary, please enlighten us – we can’t find any).
Helmets can be dangerous however, when one starts to believe the misinformation peddled in many Anglo-American road safety and helmet campaigns. A “helmet will save your life” and “It’s not safe to ride without a helmet” are dangerous ideas because 1) they aren’t true and 2) they alter cyclist & non-cyclist behaviour in ways that lead to increases in cycling collisions and injuries.
Cyclists who think they are more protected than they really are take more risks. Motorists who think cyclists are safer than they really are expose them to more risks. And of course, politicians who promote helmets as a panacea for bike safety, while ignoring the causes of road-related injuries, put cyclists at much greater risk. Not to mention the subconscious effect of portraying cycling as inherently dangerous – ‘dangerising’ it – when it is as safe as walking.
So perhaps it would be more accurate to state that while helmets are not dangerous per se, the over-promotion of their effects and mandating their use most certainly is dangerous.
Hat tip to @vebah for the photo
Update: It seems some helmet makers are now publicising the dangers of DAI. The European Road Safety study (COST327) into motorbike head injuries found the majority of serious head injuries were caused by rotational forces!