Written by Zoe Kross | ComSciCon Flagship 2026
Nearly a third of biomedical articles that report “gender differences” are measuring something else: sex. A review of 302 biomedical articles found that 29% of studies reported sex-based findings under the label of gender. But sex and gender are not the same thing: biological sex refers to a person’s reproductive features, whereas gender refers to how a person self-identifies depending on social factors and influences. Treating these as synonymous is not just careless but can also undermine the reliability of findings themselves. But there is an easy fix: scientists just need to ask participants to report both biological sex and gender identity. If the solution really is this simple, this raises the question: why do scientists continue to conflate sex and gender?
This is a systemic problem. The synonymous use of sex and gender is common in health-related government guidelines and regulations, so it is not surprising that scientists have adopted this practice as well. For example, the U.S. Food and Drug Administration (FDA) rule entitled Investigational New Drug Applications legally requires that applications for approval of new drugs contain “effectiveness and safety data for important demographic subgroups, specifically gender, age, and racial subgroups”. Further, sex and gender were not widely treated as distinct categories in medicine until 2018, when the 20th edition of the popular medical textbook, Harrison’s Principles of Internal Medicine made that distinction.
Even with this advancement, many common practices and legal frameworks continue to treat sex and gender as interchangeable. Executive order 14168, for instance, requires federal employees to use the term “sex” and not “gender” in all applicable federal policies and documents. Following this 2025 order, the U.S. Department of Health and Human Services (HHS) now only recognizes biologically male and female individuals. The HHS directly shapes federally funded research, therefore only reporting biological sex as male or female miscategorizes intersex people and excludes nonbinary and transgender individuals. Aside from being an exclusionary practice, this will likely result in lower-quality, misinformed research, by forcing researchers to make assumptions about what the findings mean, rather than interpret what the data actually shows. When government and health agencies use sex and gender interchangeably — and the scientific community reinforces this confusion by using these terms synonymously — policymakers and the public can become confused. This confusion can ultimately become dangerous.
Yet research involving human participants continues to use sex and gender interchangeably, often without explaining how either was determined, making findings difficult to interpret.
For example, my work focuses on how the menstrual cycle may influence mood. If an article reports “gender differences” in menstrual-cycle research, I assume that the authors likely mean sex differences, as menstruation is a biological process tied to sex characteristics rather than gender identity. Conversely, if an article reports “sex differences”, but measures gender, I may assume the authors mean “sex”. In both cases, I am left interpreting what the researchers intended rather than what they measured.
I am not the first person to hesitate when interpreting results when sex and gender are used interchangeably. An article reviewing sex differences in affective disorders (e.g., depression, anxiety disorders) mentioned having to assume the papers they discussed viewed gender as synonymous with sex. The authors also noted the dangers of this assumption, especially when biological sex and self-identified gender differ.
This is a particularly important issue for health-specific research. For example, gender differences in public health may stem from social determinants of health issues, whereas sex differences in public health are related to sex-specific issues, such as the manifestation of a disease. If scientists were to properly distinguish between sex and gender, this distinction could give way to new comparisons and findings, particularly those related to social and sex-specific determinants of disease.
When scientists use sex and gender interchangeably, this not only questions the reliability of findings, but also excludes people from research. From a simple statistical point of view, if scientists continue to use these terms interchangeably, then one cannot claim that reported findings generalize to a population if members of that population are excluded.
The solution is simple: ask participants to report both biological sex and gender identity. Other academic fields already do so. If we make asking about both sex and gender a standardized practice, institutional review boards, funding agencies, and governmental agencies, like the FDA and HHS, may eventually require this level of specificity. There are only benefits to this practice, as distinguishing between sex and gender will result in more inclusive research, richer datasets with more variables of interest, and less confusion in reported findings. Scientists have the power to make science more inclusive and stronger. It’s a simple fix: just ask the extra question.
Author Bio
Zoe Kross is a Ph.D. Student in Psychology at Northeastern University in Boston, MA. Her research focuses on how fluctuations in ovarian hormones (i.e., the menstrual cycle) and suppressions in ovarian hormones (i.e., hormonal contraceptive use) influence adolescent behavior and brain development. Zoe is also interested in science communication, accessibility, and policy, particularly regarding misinformation around reproductive health. Outside the lab, she has participated in the ComSciCon Flagship Workshop in Bordeaux and enjoys reading and hiking in her free time.
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