Sexism's Threat to Human Health

Sex-related differences in research

Posted Oct 02, 2014

I grew up thinking of sex-related differences as being my mom telling my dad that if he didn't turn off the baseball game and go cut the lawn they would be on the 6 o'clock news. In science it is something different. Most scientific research does not consider sex-related differences, which is problematic and scientifically curious. However, ignoring females’ needs is congruent with out social treatment of women. Aside from the occasional female-dominated culture or random monarch, men have ruled the world while women picked up the pieces, the kids, the socks, the dry-cleaning, and whatever else needed to be picked up. Likewise, men have controlled medicine and science, which caused research to be so male-centric that even the pre-clinical trials are usually only done on male animals.[1] 

The sex of the cell makes a huge difference, because the pre-clinical studies, where we’re testing drugs or therapies, are those studies that build the evidence base and inform the clinical studies. So if you are going to be studying a disease that affects both men and women, it’s really important to think about male and female cells and males and females in the animal model work when you are doing that pre-clinical research,” says Janine Clayton, M.D., Director, of the National Institutes of Health - Office of Research on Women’s Health[2]

Most often, not looking at sex-related differences in research is careless science. You cannot describe a rock accurately by only looking at one side of it. Why would you attempt to describe research in a sexually dimorphic species by only looking at one half of the species? However, because we have done precisely this, we are now finding vital information about the X & Y chromosome that are revolutionizing our treatment strategies in neurodegenerative conditions such as Multiple Sclerosis, Parkinson’s disease, schizophrenia and stroke. If there are differences in these areas, there will be differences in other areas—obviously, which is why the NIH - ORWH is directing its attention to sex-related differences.[3]

Cannot Blame It All on Men

There are no victims, only volunteers. Regrettably sexism in science doesn’t just come from men. In 2012, the Proceedings of the National Academy of Sciences (PNAS) reported a study that asked faculty members to review hypothetical students' resumés  and determine the likelihood of their  hiring that student, and the starting salary. The only differences in the resumés were the first names at the top of the page: Jennifer and John. Across the board, John got higher ratings and his median salary was $3,000.00 more than Jennifer’s. Both male and female faculty members were biased against Jennifer. This may contribute to the deficit of women in science, which conceivably contributes to the sex-bias in research.[4]  Some find it curious that the women in this study were as sexist as the men; I do not. The worst aspect of discrimination is what it teaches you to think about yourself.  

Doing the Math

With the many great scientists we have, I find it curious that sex-related differences would not be automatically factored into the basic research design of most studies. Just based on the mathematical concept of symmetry alone, which allows us to classify different types of regular patterns and distinguish between them, scientists should know better than to exclude sex-related differences. Excluding sex-related differences is similar to dropping a pebble in a pond. The dissipating concentric circles appear to form a symmetrical pattern, but in actuality the intrusion of the pebble disrupts the symmetry of the surface plane of the pond. We see a pattern because the disruption is not complete. Likewise, in male-centric research we are vulnerable to seeing a pattern because the pattern is not complete, as opposed to because the pattern in significant. In some cases, as we are finding out, presuming these patterns are actual legitimate scientific evidence is incorrect and to our detriment.

The facts are simple. We are a dimorphic social species. The decibel and clarity at which the data can speak is dependent on the resonance of the research design, which is attenuated when sex-related differences are excluded. Therefore, until women’s health is given equal consideration, men’s health is not being fully considered.

“Our Center has been looking at sex differences since the beginning so it’s been part of our culture to think about it, but many scientists have had their heads in the sand on this topic for a long time – it’s amazing that it’s been so long before the scientific community really confronted it,” says Kirsten Tillisch, M.D. from the Center for the Neurobiology of Stress (CNS) at UCLA. This vanguard facility, is among a very few elite research groups that has consistently focused on sex-related differences.

 Emeran Mayer, MD PhD, Director of UCLA CNS, who has studied sex-related differences in brain-gut interactions for many years, says, "With support from the National Institutes of Health Offices of Research on Women’s Health and National Institute of Digestive Diseases and Kidney we have been studying sex-related differences in chronic visceral pain conditions such as IBS and Bladder Pain Syndrome/Interstitial Cystitis for more than 10 years.”  Mayer goes on to add, “The remarkable insights that have been gained from these studies is that sex really matters. For example, structural and functional alterations in the brain of patients suffering from these disorders are often more pronounced when comparing male and female patients, or male and female healthy controls, than between patients and control subjects in general. These findings imply that treatments develop for many of these chronic pain conditions have different targets in the brain depending on the sex of the patient. It also is consistent with the clinical observation that often men and women will respond differently to the same medication when given at a standard dose," Dr. Mayer explained. 

When you walk into the UCLA Center for the Neurobiology of Stress, you immediately notice two things: 1) every one is extremely busy and 2) it is mostly women. Mayer says this is because, “The focus of our center on studying sex-related differences has attracted a large number of young female investigators who for the first time get an opportunity to find out what is unique about the female human brain in chronic disease." 

They say the hand that rocks the cradle, rules the world. What hen becomes of the cradle if the motion of that hand is ragged from MS, trembling from Parkinson's, or stilled by a strke because we failed to conduct meticulous research that observed sex-related differences. This is not a matter of being politically correct; it is a matter of being scientifically correct. Remain Fabulous and phenomenal! 

*All images purchased by UCLA Geffen School of Medicine - Brain Research from Shutterstock, for use and alteration by Dr. Gordon,

Sidebar: Not surprisingly, Psychology Today was recently chosen as the top Psychology Website; Very surprisingly, I was chosen as one of the "30 Most Influential Neuroscientists Alive Today" I am so honored by this, and I truly believe this is largely because of the unwavering support of my readers and Psychology Today. So this really belongs more to you guys than me. Thank you. - Billi 

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1.      Zucker, I. and A.K. Beery, Males still dominate animal studies. Nature, 2010. 465(7299): p. 690.

2.      Woodrff, J. NIH orders scientists to test new drugs on animals of both sexes.  [cited 2014 May 20, 2014]; Available from:

3.      Clayton, J.A. and F.S. Collins, Policy: NIH to balance sex in cell and animal studies. Nature, 2014. 509(7500): p. 282-3.

4.      Moss-Racusin, C.A., et al., Science faculty's subtle gender biases favor male students. Proc Natl Acad Sci U S A, 2012. 109(41): p. 16474-9.

About the Author

Billi Gordon, Ph.D., is a co-investigator in the Ingestive Behaviors & Obesity Program, Center for the Neurobiology of Stress, David Geffen School of Medicine at UCLA.

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