There seem to be fundamental differences in how males and females process painful stimuli. According to a report published by Live Science, in order for a person to feel pain, sensory neurons known as pain receptors detect painful stimuli and then send a signal to the brain for interpretation. These painful stimuli include extreme temperatures, mechanical pressure, and inflammation. The way each individual perceives these stimuli varies according to different factors including the person's gender. Many studies have reported that women have a higher sensitivity to pain and a lower pain threshold than men. For instance, a 2012 study that examined how men and women respond to physical pressure found that women are more sensitive to mechanical pain than men. In another study, men and women were asked to signal when they felt a thermal stimulus and to rate its intensity. The study indicated that women's pain threshold for heat is lower than that of men.
Jeffrey Mogil, a professor of behavioral neuroscience at McGill University who studies sex differences in pain, stated, "It is known that females are more sensitive to pain than males," adding that this is a result that has been established in hundreds of studies "however, not all are statistically significant, yet they all move in the same direction." Nevertheless, some studies show the opposite. In a study published in 2023, researchers selected 22 teenagers - 12 females and 10 males - to test thermal pain sensitivity. These participants were exposed to hot and cold stimuli and then asked to rate their pain intensity. Males rated the severity of pain for both stimuli higher than females. Additionally, results from other studies indicated no differences in how males and females respond to pain-inducing heat.
Frank Boric, a professor of neuroscience at the University of Arizona, explained that the discrepancies among scientists and the results of scientific studies stem from the lack of "meaningful" measures to assess pain tolerance. Pain threshold and individual tolerance tend to vary across tests and environments; some studies have also found that females are more reliable in testing than males, as they provide more consistent ratings of their pain.
Boric studied the mechanisms that could enhance pain and discovered recently that pain receptors in males and females are activated by different substances, meaning that the first step in perceiving pain differs between genders. Mogil mentioned that he has never shown that the characteristics of pain receptors themselves depend on gender. It is known that painful stimuli need to exceed certain thresholds to activate pain receptors. Typically, low-intensity stimulation, such as drinking cold water, does not activate pain receptors - but if a person has an ulcer in their mouth, the pain receptors there will activate. In this context, Boric explained that the activation threshold of pain receptors is lowered, and it can then be determined whether this "sensitivity" depends on gender.
To test the validity of this hypothesis, researchers sampled pain receptor cells from the dorsal root ganglion, a station near the spinal cord through which sensory information travels to the central nervous system. They collected cells from male and female mice, non-human primates, and humans and exposed the cells to different substances. Previous studies have indicated the involvement of the hormone prolactin in the female response to pain and a chemical messenger called orexin in pain responses in males, so these seemed like ideal factors for experimentation. The results showed that the cells behaved differently when exposed to either substance across all sampled species.
Prolactin lowered the activation threshold of pain receptors in females but had no effect on males. Conversely, orexin made male cells sensitive but had no effect on female cells. Both substances naturally exist in both genders but at different concentrations. Boric stated, "The pain receptors we derive from male or female animals or human donors post-mortem differ entirely in the processes that produce this decrease in thresholds." He added that this discovery could help develop pain treatments that can be optimized for men and women, especially since "most pain patients in the world are women." For example, chronic pain conditions like fibromyalgia are more common among women than men in the United States. Mogil concluded, "Regardless of which gender is more sensitive to pain, there is increasing evidence that the underlying circuits are different between males and females."
