>>1156304You know that a helmet can kill you as well, right? What causes most of the concussions and deaths in these circumstances are rotational forces, not direct impacts, and helmets not only offer 0 protection against them but extend the radius of your head. Others die strangled by the strap (mostly children).
Protect yourself against these fringe cases and don't wear a helmet.
The reality is that that there's not solid evidence for or against helmets, you might as well wear a crucifix. Here's but one example
https://www.sciencedirect.com/science/article/abs/pii/S000145750200012X 