Being diagnosed with cancer can be scary. But how useful is that fear? Sometimes, the fear that patients feel at diagnosis can harm them as much as the disease does, says David Ropeik, risk perception expert and Harvard University Extension School instructor. Over at Nature's Soapbox Science guest blog, Ropeik says "cancer phobia" can be bad for one's health. It can contribute to over-diagnosis and unnecessary treatments like surgery or radiation, he adds.