Why Are Some People Transgender?

This week, by request from listener Cindy in Iowa, we’ll take a look at the still-evolving science of what causes an individual to be transgender. Plus, the surprising reason why gender dysphoria is a mental disorder.

Ellen Hendriksen, PhD,
Episode #116
holding sign at protest

Factor #1: Genetics. In a 2012 review, researchers scoured the world for twins in which one or both twins were transgender. In the identical twin pairs, meaning twins with exactly the same genetic information, 39% were both transgender. Of the fraternal twins, where each sibling is genetically unique, how many were both transgender? Exactly zero. The much higher likelihood of both twins being transgender if they are identical versus fraternal implies that genes play a role in determining transgenderism.  What’s more, a study in the journal Biological Psychiatry actually found a gene variant that was associated with being a trans woman like Laverne Cox or Janet Mock.

Factor #2: The Uterine Environment. But wait, you say, shouldn’t identical twin pairs be the same? If one identical twin is transgender, shouldn’t the other? How do you account for the 61% of identical twin pairs where only one is trans? Again, the scientific jury is still out, but a probable answer lies in the prenatal environment, aka the womb. Identical twins may share genetic codes, but their epigenomes—which of the genes get expressed or remain unexpressed—diverge. Let’s not forget that identical twins have separate umbilical cords, usually have separate amniotic sacs, and develop in different locations in the womb. All these factors can affect the exact dispersion of nutrients, chemicals, and, most importantly, hormones.  

Factor #3: Brain structures. Since brains are further shaped by experience, neuroimaging of adult trans brains have to be taken with a grain of eyeliner. That said, a 2014 study in the Journal of Neuroscience found that differences in the brain’s white matter tracts fell along a perfect spectrum of gender identity with cisgender men and women at the ends and trans men and women in the middle. 

One important note is that a factor not on this list is nurture. So far, the role of the environment seems to be tiny. 

One important note is that a factor not on this list is nurture. So far, the role of the environment seems to be tiny. Back in the day, a transgender identity was thought to be the result of some sort of early trauma. Families, especially mothers, were wrongfully blamed. But as biological evidence mounts, the role of the environment shrinks, which explains why conversion therapies, whether for gender identity or sexual orientation, are increasingly considered ineffective at best, and harmful at worst.

OK, so if gender identity is biological and set before birth, why is there a mental health diagnosis associated with being transgender? Doesn’t that imply that something is wrong? Well, yes and no. To truly be a disorder, a psychological issue has to cause distress, meaning significant negative emotion, or impairment, meaning it gets in the way of living your life.  The “bible” of mental health professionals, the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, affectionately nicknamed DSM-5, does include Gender Dysphoria as a diagnosis. But, it makes it clear that gender identity isn’t the problem; the distress and impairment come from living with an assigned gender that’s different than one’s experienced gender. In other words, being transgender isn’t a disorder; transgender individuals know who they are, but they have to deal with an often hostile society. That’s the dysphoria.

After much deliberation (and more than a little fighting), Gender Dysphoria was included in the DSM5, replacing Gender Identity Disorder, which pathologized the mismatch of assigned sex and gender identity, much like the DSM-II pathologized homosexuality. The new Gender Dysphoria diagnosis gives transgender individuals a diagnosis that allows them to receive the health care they need, from counseling services to hormone treatment to gender transitioning procedures. The diagnosis provides a safeguard and connects transgender individuals with care, especially in a health care system where insurance companies require a diagnosis code before approving a penny.  

Or course, there’s still ongoing fighting about whether or not it’s appropriate to diagnose an individual when the distress comes from a culture that stigmatizes people who don’t conform to gender norms. We’ll see if DSM-6 changes things yet again, but for now, many see the diagnosis as an important practical and symbolic step.

So stay tuned for more research on the biology of gender. Right now it’s still getting started, but it promises to be richer than Jennifer Pritzker, who, by the way, is the world’s first transgender billionaire.

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