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New Featured Article: Defining Biological Sex

Sex differences in the human brain: a roadmap for more careful analysis and interpretation of a biological reality
A note from the Editor-in-Chief, Jill B Becker
Defining biological sex by gonadal and chromosomal characteristics at birth, multiple large datasets reflecting current best-practice show convergent evidence for small to moderate sex differences in human brain volume above and beyond sex-differences in brain size. For example, M>F in putamen, amygdala, hippocampus, and temporal pole volume, F>M in volume of the cingulate, superior parietal, and lateral prefrontal cortices. In contrast, reviews of past studies obscure this consistency because methodological heterogeneity is not accounted for. We do not yet know if any of the reproducible sex-differences in regional human brain anatomy have any functional implications. Separate studies would be required to address this hypothesis. There also diverse biological, psychological and social factors that could contribute to regional sex-differences in human brain anatomy. Untangling these causes is hard in humans, but may be helped by research in animal models. Finally, the existence of sex-differences in human brain anatomy is based on comparisons between two groups defined by biological sex (often self-reported). This frame of reference does not address intersex conditions, gender diversity or intersectional identities. However - with these boundaries in mind -  we conclude that stratifying people based on biological sex does identify reproducible sex-based group differences in regional brain volume. The best evidence to date suggests that these differences are a biological reality, but that more work is needed to understand their causes and (if any) functional consequences. We also argue that the laden nature of sex and gender in history and society mean that  - despite the idealized objectivity of the scientific method - reports of sex-based differences in the human brain should be disseminated in a pro-actively anti-sexist manner. We offer this Commentary from DeCasien et al regarding sex-based differences in the human brain and argue that it is not sexist to discuss sex differences in the human brain. In fact, it is pro-human to understand where there are and where there are not differences in the human brain based on the sex of the individual.

New special collections now publishing

Read more about our newly launched special series on the topics of Sex Differences in Development and Sex Differences in COVID-19.

Aims and scope

Unlike any other scientific journal, Biology of Sex Differences focuses on sex differences in all aspects of an individual or organism: from molecules to behavior and from studies of cellular function to clinical research studies. This journal aims to improve understanding of basic biological principles mediating sex differences and foster development of therapeutic and diagnostic tools that are sex-specific. To the extent that gender influences biological outcomes, this journal also is interested in research addressing gender differences. Articles are expected to report results that directly compare sex/gender differences in the statistical analysis.

Biology of Sex Differences is the official journal of the Organization for the Study of Sex Differences, and a publication of the Society for Women's Health Research.


Upcoming Collections


Sex Differences in COVID-19
We welcome submissions of original articles and reviews on preclinical and clinical research in which findings of new sex differences in COVID-19 are reported. We are particularly interested in studies in which potential mechanisms are tested.

Sex Differences in Development
We are interested in primary research or review articles that address sex differences in development that are influenced by environmental, social, genetic, hormonal, or other biological factors. Outcome measures may include brain, behavior and/or physiological processes in children/adolescents or animal models of these processes.


Sex differences in response to androgens: physiological and pathophysiological 
Guest Editor: Licy Yanes Cardozo

Hypertension, preeclampsia, renal and cardiovascular disease in pregnancy
Guest Editor: Vesna Garovic


Sex Differences in Obesity, Insulin Resistance, Metabolic Syndrome, and the Microbiome
Guest Editor: Kate Denton


Jill BeckerUniversity of Michigan, USA

Associate Editors
Jeanette H. MagnusFaculty of Medicine, University of Oslo
Licy L. Yanes Cardozo, University of Mississippi Medical Center

Founding Editor
Arthur P Arnold, University of California, Los Angeles, USA

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Rhonda Voskuhl, M.D. President of the OSSD

Message from the OSSD President

Rhonda Voskuhl, M.D., President of OSSD

Rhonda Voskuhl M.D. is the current President of the OSSD. She holds the Jack H. Skirball Chair and is a Professor in the Department of Neurology and the Director of the Multiple Sclerosis Program at the David Geffen School of Medicine, University of California, Los Angeles (UCLA).

To read about some of the latest work by Dr. Voskuhl click here.

The Organization for the Study of Sex Differences (OSSD) is an international research society focused on the study of sex as a biologic variable in health and disease. Our members have tremendous expertise in a vast array of disciplines within science and medicine, linked by the common theme of the study of sex differences. Our annual meeting brings together these investigators to share mechanistic insights underlying sex differences to promote thinking outside the box of each specific discipline. OSSD also does advocacy and education regarding the importance of understanding sex differences that can translate into novel treatments optimally tailored for each sex for the benefit of both women and men. The Biology of Sex Differences is the official journal of the OSSD and a partner in this shared mission.

Affiliated with

  • Society for Women's Health Research

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