Professor John Ryan:

A number of points have been made and there is some overlap, so I will touch on some of them and other colleagues will touch on others. The evidence, particularly in the sport of rugby, around scrum caps shows that they will protect the scalp but not the brain. There is anxiety in some circles that it may give younger children a false sense of security, allowing them to lead with the head and use it as a weapon because it is now protected. The structure one wants to protect is the brain inside of it, but what one is protecting is the scalp. In some sports the weight of a heavier helmet may put an abnormal torque on the neck and even put the neck at risk. There are studies evaluating the true benefits of protective head gear in sport.