It's difficult to say. Again, there is no evidence on this. Some of the impact certainly would be absorbed by the helmet, but I wouldn't go so far as to say that a helmet would be protective to any significant degree. Helmets are used in amateur boxing, but there are also a number of other different rules, so the rates of concussions and head injury in amateur boxing are much lower. It's hard to say whether helmets alone would have a significant effect. They probably would be helpful, but it's difficult to say.
On April 15th, 2013. See this statement in context.