MOGILab was the first to demonstrate a qualitative sex difference in pain mechanisms, and has continued to find new examples of sex differences in pain, most quite by accident, simply by always using both sexes in experiments. By demonstrating such sex differences, we have encouraged the field to stop avoiding the use of female subjects (who do not display more variable data than do males).

Quantitative Sex Differences

Although sex differences in pain depend on the genetic background of the subject (see below) and the modality and intensity of the noxious stimulus, MOGILab has re-analyzed the available human evidence to show beyond any doubt that (in contrast to most people’s intuitions on the subject) women are more sensitive to pain than men. It doesn’t matter what type of pain is considered, nor how that pain is measured. Women are also more likely than men to endorse having chronic pain symptoms, and as a result represent the clear majority of chronic pain patients. In preclinical studies, although quantitative sex differences are often observed, often they aren’t, and we have shown that sex accounts for far more variability as a factor interacting with other factors (e.g., strain, environment) than it does by itself.

Genotype-Sex Interactions

Genotype (i.e., genetic background) and sex interact, such that sex differences are only observed in some genotypes and some genotype differences are only observed in one sex. Notable interactions demonstrated by MOGILab include the following:

Qualitative Sex Differences

MOGILab is continually demonstrating that in addition to the existence of quantitative sex differences, in which male and female mice have different amounts of pain or analgesia, males and females process pain in a remarkably independent fashion. The following qualitative sex differences have been demonstrated (in chronological order):

Current Projects

In a paper currently submitted, we look at even longer time points after injury (almost 3 years in a few mice), and find a sex-specific impact of chronic pain on mortality in the mouse. Stay tuned!

Reviews

The following review papers summarize the field of sex (and gender) differences in pain, published in: 1999, 2000, 2004, 2007, 2010, 2012, 2017, 2018a, 2018b, and 2020.