Actually no.
There was a very major 21 year research study by the University of New South Wales released within the past ten days or so that indicated the use of helmets had brought about a statistically significant drop in head injuries
If you want to read the study the correct link for it is http://unsworks.unsw.edu.au/fapi/datastream/unsworks:10700/SOURCE01
Its a particularly poor study. They measure the cyclist head injuries per 100,000 population - a rather useless measure as it takes no account of variations in the level of cycling in the population over the 21 years. They do sort of recognise this problem but since they don't have the data on the level of cycling (although I don't know why as the data is available), they use the number of bikes imported into Australia each year as a measure of the level of cycling taking place. Which misses the fact that most bikes sold are used once or twice and then left to rust in the shed and that most cyclists are riding bikes that were not bought this year. So the end results that they come up with are pretty close to meaningless but they do support the authors preconceptions, the main author being, you guessed it, from the Land of the Helmet Cult, the USA.