Bicycle helmets most definitely will reduce your risk of death or a serious head injury in the event of an accident. No one disputes this. Anyone arguing the contrary is frankly just wrong. If you had a choice between wearing a helmet and not wearing one and being struck by a car on a bike, you would be a moron to not wear a helmet.

The argument against helmets, however, is the effect of compulsory helmet laws. In those countries where this has been implemented, the result is a substantial drop in the uptake of cycling in the community. Apart from negative public health implications of a more sedentary lifestyle, a reduction in the number of cyclists on the roads leads to an increased risk to the remaining cyclists. For the most part, the introduction of compulsory helmets has a deleterious effect on the overall population (despite the reduction of serious head trauma as a proportion of cycling accidents).

Regards.