For many women, the old adage "better safe than sorry" has a lot of weight when deciding whether to be screened for breast cancer. However, a recent study out of Denmark says that one in three breast cancers detected by a screening mammogram may be treated unnecessarily - and cause unnecessary trauma.

The study, conducted by Karsten Jorgensen and Peter Gotzsche of the Nordic Cochrane Centre in Copenhagen, confirms that more cases of breast cancer are discovered once screening programs began. In theory, a successful screening program results in a drop in cancer detection in older women, since these cases would be caught at a screening at an earlier age. Instead, the study found that the number of cases in women aged between 50 and 69 simply grew to thousands more than were identified earlier.

Some cancers grow too slowly to affect a patient, but it's impossible to distinguish between these slow-moving cancers and those that are deadly. For this reason, any cancer found is treated.

The final diagnosis? Jorgensen and Gotzsche say there are negative consequences in treating women for breast cancer unnecessarily, including psychological damage and harmful side effects.