"Most patients who visit the doctor are female. Most patients who report being in pain are female. "The epidemiology is clear, women are up to 70 percent of all pain patients" says Jeffrey Mogil, a neuroscientist at McGill University and author of a new commentary in Nature arguing for greater diversity in lab animals. A growing body of evidence—including a 2012 analysis of 11,000 patient records—indicates that women are more sensitive to pain. In fact, they may be hardwired to feel pain differently. Last year, Magil and a plethora of co-authors published a study showing that female lab mice actually used different cells to transmit pain signals through their spinal cord. And while no one has confirmed that this is also the case in human females (paging the ethics committee...), Magil says evidence in animals is both compelling and growing stronger. "This is not news for those of us who have worked in this field for a long time," says William Schmidt, president of NorthStar Consulting, a pain research company. "It’s still a struggle to get some very traditional investigators to understand the importance of gender in preclinical and clinical pain research." In 2015, just 4 percent of all the rodent-based papers published in the journal Pain used both males and females, says Mogil. That's roughly the same as it has been for a decade Mogil says this inertia comes partly from scientists who believe female rodents aren't reliable model organisms. And true, there is research that indicates their hormonal fluctuations (female rodents have oestrous cycle that is roughly analogous to the human menstrual cycle) do affect the data. "The problem is if you look at those studies, their results are going in different directions," says Mogil. In some studies rats are more sensitive, in others less. Overall, it averages out, he says."