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Through the Gates: Sex Differences in Pain Management

Illustration by Daniel HorowitzFor most of human history, little has been known about how people experience pain—let alone how one person’s pain might differ from another’s. But recent research has illuminated the surprisingly distinct ways that individuals experience pain—and how women perceive pain differently from men. These new findings could have wide-reaching implications, according to scientists who showcased their groundbreaking research into gender-specific pain perception at Barnard during a September 2011 event titled “Roadmap for Addressing Sex Differences in Pain Management.” The event was supported and co-sponsored by Women in World Neuroscience of the International Brain Research Organization (IBRO).

“Pain is one of the most prevalent of the diseases and ailments that have sex differences,” said Rae Silver, Kaplan Professor of Natural and Physical Sciences at Barnard and organizer of the event along with Emmeline Edwards, director of extramural research at the National Center for Complementary and Alternate Medicine and chair of the Women in World Neuroscience committee, and Kathie Olsen, founder and managing director of Science Works, LLC. Said Silver, “If we understood those differences, we could better treat and anticipate diseases in both sexes.”

In opening the event President Debora Spar pointed to the importance of maximizing knowledge to improve the health benefits of pain treatment and introduced the distinguished panelists. The participants offered a range of revelations into the study of pain—from the possibility that redheaded women are more pain tolerant than brunettes to the prospect that astronauts could unveil the mysteries of gender-specific pain.

Dr. Marianne Legato, who founded and directs the Partnership for Gender-Specific Medicine at Columbia University, moderated the panel and noted that until the 1990s, most scientific research dealt with the middle-aged white male. In some cases, laws restricted the participation of women. Pain rarely received much attention from scientists, since studies of pain were largely seen as “soft” or “pseudo” science. In place of scientific knowledge, there was conventional wisdom, which held either that women are tougher because they are equipped to endure the pains of childbirth or that men are tougher because, well, they’re men. Turns out, neither stereotype is exactly right.

Women likely are more sensitive to pain in some ways, but they also have hormones that can mediate pain in ways that don’t work for men. Jeffrey Mogil, the E.P. Taylor Chair in Pain Studies and Canada Research Chair in Genetics of Pain at McGill University, explained: “Males and females have qualitatively different pain-processing mechanisms; that is, difference in kind, not in degree.” His research of the neural mechanisms that mediate the perception and inhibition of pain has indicated that women might have fewer mu-opioid receptors, which respond to morphine. This difference might explain why women typically need higher dosages of pain medications.

Dr. Mogil also found connections between the gene that accounts for red hair color in 80 percent of natural redheads and how those redheads perceive pain. A study he conducted with redheaded mice found that redheaded females could tolerate significantly more pain than other females or redheaded males. “These strong and robust brain differences in pain processing are going to leadto differential pain treatments,” he predicted.

A major value of research into perceptions of pain is the potential to find better ways to alleviate it. Dr. Richard Smiley, a professor of clinical anesthesiology and chief of obstetric anesthesia at Columbia University Medical Center, said that his research into the genetics of labor pain suggests oxytocin might protect pregnant women from the development of chronic pain. Oxytocin is a hormone released in women during and after childbirth and while breastfeeding, and has been associated with creating emotional connections.

Finding effective ways to treat pain experienced by women is especially important since 70 percent of those who suffer from chronic pain are women. Though oxytocin produced naturally by the body can prevent chronic pain in some cases, it cannot be used to treat it, said Dr. Smiley.

Fortunately, there are other possible solutions. Dr. Josephine Briggs, director of the National Center for Complementary and Alternative Medicine, discussed non-pharmacological interventions for chronic pain, such as complementary and alternative medicine. One study found that people with chronic pain who practiced mindful meditation suffered with substantially less severity than those who did not.

The human body may be the focus of pain research, but the new frontier of such research, according to Dr. Saralyn Mark ’83, is outer space. “Turns out, it’s easier to discern differences in sex and gender-based health care in space because you can discern those differences very fast and in a way that you often cannot on Earth,” said Mark, an endocrinologist, geriatrician, and women’s health specialist.

Studies of pain in space have already proven fruitful. One revealed that almost all female astronauts begin to experience orthostatic hypotension, meaning they feel like they’re going to faint, when they return to earth. This may be due to differences in how the body adapts to microgravity and readapts to earth. “When women are stressed, they tend to increase their heart rates, whereas men tend to clamp down,” she said.

Thanks to female lab subjects, redheaded mice, research in space and the pioneering studies of the panelists, a window is opening onto one of the most intense of human experiences. As scientists understand more about the relationship between gender and pain, people’s experience of pain—and especially women’s—could become a lot less painful.

—by Deenah Vollmer