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COMMENT
Sex and Gender Are Distinct Variables Critical to Health: Comment on
Hyde, Bigler, Joel, Tate, and van Anders (2019)
Michelle A. Cretella
American College of Pediatricians
Christopher H. Rosik
Link Care Center, Fresno, California,
and Fresno Pacific University
A. A. Howsepian
University of California, San Francisco
In this brief comment on Hyde, Bigler, Joel, Tate, and van Anders (2019), we maintain that
sex and gender are distinct variables that impact human health in critical ways both
individually and interactively. In the life sciences, sex is defined by how an organism is
organized with respect to reproduction. Among humans, reproduction requires the union of
two distinct gametes. Hence, human sex, in contrast to gender, is an innate and immutable
biologically binary trait that is not fundamentally determined or altered by psychosocial
factors. The existence of congenital disorders of sex development, typically associated with
reduced fertility, does not negate the human sexual binary as defined by the life sciences.
Individuals who identify as transgender remain either biological males or females. Diseases
that affect both sexes often have different frequencies, presentations, and responses to
treatments in males and females; therefore, different preventative, diagnostic, and treatment
approaches may be required for males and females. For the sake of all people, especially those
who identify as transgender, we must move forward in examining the gender binary without
jettisoning the reality and importance of sexual dimorphism in psychology and medicine.
Keywords: sex, binary, transgender, spectrum, intersex
Examination of the gender binary is important and we
applaud Hyde, Bigler, Joel, Tate, and van Anders (2019) for
initiating the process here. We are among those who make
a clear distinction between sex and gender (Hyde et al.,
2019, p. 172) while recognizing the two variables are in-
trinsically linked. We do not believe that the sex binary
excludes a spectrum of gender expression, and disagree that
overlapping physical, physiological, and psychological fea-
tures between the sexes negates the sex binary. We are
concerned by Hyde et al.’s conclusion that reliance on
categories of male and female in research is an obstacle to
scientific progress (p. 183). There is substantial evidence to
suggest the opposite—that treating “sex/gender” as a single
variable on a spectrum is contrary to science. To further the
conversation, we share some findings from the life sciences,
genetics, and gender-specific medicine as evidence that the
sex binary exists and is consequential to human health.
First, sex has been defined as a biological trait that
distinguishes living things as being male or female as de-
termined by both genes found in the complement of sex
chromosomes and by the presence of distinctive reproduc-
tive organs (American Psychiatric Association, 2013,p.
829; Institute of Medicine [IOM], 2001). This definition is
not arbitrary. In the life sciences, sex is defined by how an
organism is organized with respect to reproduction. Hu-
mans, like all mammals, require two gametes to reproduce:
ova produced by females and sperm produced by males.
Hence, human sex is an innate binary biological trait that is
not fundamentally determined or altered by psychosocial
factors. Hyde et al (2019, p. 172) raise the reality of intersex
conditions to suggest there is a spectrum of human sexes.
However, these do not represent additional sexes because
Michelle A. Cretella, American College of Pediatricians; XChristopher
H. Rosik, Link Care Center, Fresno, California, and Department of Psy-
chology, Fresno Pacific University; XA. A. Howsepian, Fresno Medical
Education Program, University of California, San Francisco.
Correspondence concerning this article should be addressed to Christo-
pher H. Rosik, Link Care Center, 1734 West Shaw Avenue, Fresno, CA
93711. E-mail: christopherrosik@linkcare.org
This document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.
American Psychologist
© 2019 American Psychological Association 2019, Vol. 74, No. 7, 842–844
ISSN: 0003-066X http://dx.doi.org/10.1037/amp0000524
842
they do not constitute additional gametes or reproductive
systems. In fact, each of these rare disorders are associated
with reduced fertility (Słowikowska-Hilczer et al., 2017).
Second, although gender is inextricably linked to sex,
gender is not an innate and immutable biological trait like
sex. There are no biomarkers for gender or gender identity
because these are heavily socially and psychologically in-
fluenced concepts. Gender identity is an awareness of, and
comfort level with, one’s sex. Gender identity, like every
identity, is a product of the mind that may be influenced by
biological factors but is not solely determined by them.
Consequently, gender identity, unlike sex, may change.
Children with gender dysphoria, for example, will come to
identify with their biological sex in 61% to 98% of cases by
adulthood (Ristori & Steensma, 2016). Moreover, remission
has also been observed among adults (Marks, Green, &
Mataix-Cols, 2000).
Third, research suggesting that the human body reflects
“sexual mosaicism” rather than a sexual binary, some of
which Hyde et al. (2019) review (pp. 173–176), is refuted
by modern genetics and gender specific medicine. Although
males and females have more traits in common than not,
genes present on sex chromosomes at fertilization impart
significant innate molecular differences between men and
women in every nucleated cell of the body and, therefore, in
every organ system (IOM, 2001). In addition to sex-specific
genes found on the sex chromosomes, scientists have iden-
tified at least 6,500 shared genes that are expressed differ-
ently throughout the body depending on whether the subject
is male or female. This sex differential gene expression has
been identified in at least 53 different tissues, including
brain tissue (Gershoni & Pietrokovski, 2017). In other
words, macroscopic similarities between male and female
body systems notwithstanding, organ tissues are sexually
dimorphic at the molecular/hard-drive level due to sex spe-
cific genes and sex differentially expressed genes that are
present at fertilization (Gershoni & Pietrokovski, 2017).
In fact, brain gene transcription has been found to be
sexually dimorphic across the life span, and the biggest
male–female difference for many genes occurs during the
prenatal period (Kang et al., 2011). Some of these genetic
differences translate into dynamic structural differences.
For example, neural connections between subcortical and
cortical structures undergo profound alterations as a func-
tion of gestational age in female fetuses but not in male
fetuses (Wheelock et al., 2019).
Finally, the importance of biological sex differences in
health care has been recognized for nearly two decades
by the IOM (2001). Sex-based genetic differences ex-
plain disparities between men and women in their (a)
propensity for developing certain diseases; (b) responses
to drugs, toxins, and pain; (c) cognitive and emotional
processing, and more (IOM, 2001;Legato, Johnson, &
Manson, 2016). The ongoing consideration of biological
sex differences in medicine is absolutely necessary to
improve patient outcomes. For decades, women were
treated as smaller versions of men, sometimes resulting
in their untimely demise. For example, a woman with the
irregular heart rhythm atrial fibrillation has a higher risk
of suffering a stroke than a man with the condition, and
her stroke is more likely to be hemorrhagic. Critically,
she is also at greater risk of experiencing sudden death
from some of the drugs typically administered to treat
that arrhythmia (Legato et al., 2016). This is why the
field of gender-specific medicine approaches sex and
gender as distinct, though intrinsically related, variables
that impact human health in critical ways both individu-
ally and interactively.
Those who identify as transgender remain biological
men and women. All men and women, including those
who identify as transgender, deserve optimal medical
treatment which is uniquely affected by their biological
sex. Diseases that affect both sexes often have different
frequencies, presentations, and responses to treatment in
males and females, therefore potentially requiring differ-
ent preventative, diagnostic, and treatment approaches
based on sex (IOM, 2001;Legato et al., 2016). For these
reasons and more, reorganizing psychological and med-
ical care around a flawed concept of a single sex/gender
variable will cause serious harm to many patients. For the
sake of all people, perhaps most especially those who
identify as transgender, psychologists, health profession-
als, and researchers must maintain a distinction between
“sex” and “gender,” as each represents a separate vari-
able critical to human health. Conversation concerning
the gender binary will continue, but we abandon the
reality of the sex binary at our peril.
References
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This document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.
843
COMMENT: SEX AND GENDER ARE DISTINCTLY CRITICAL TO HEALTH
Marks, I., Green, R., & Mataix-Cols, D. (2000). Adult gender identity
disorder can remit. Comprehensive Psychiatry, 41, 273–275. http://dx
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Romero, R., Eggebrecht, A. T., & Thomason, M. E. (2019). Sex differ-
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.1016/j.dcn.2019.100632
Received May 3, 2019
Revision received July 19, 2019
Accepted July 22, 2019 䡲
This document is copyrighted by the American Psychological Association or one of its allied publishers.
This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.
844 CRETELLA, ROSIK, AND HOWSEPIAN
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