Gender dysphoria has a partial genetic basis, but no single gene determines it. Twin studies consistently show that genetics account for somewhere between 11% and 70% of the variation in gender identity outcomes, depending on the study and how gender identity is measured. The wide range in those estimates tells you something important: genes matter, but they’re far from the whole story. Prenatal hormones, epigenetic changes, and still-unknown environmental factors all appear to play a role.
What Twin Studies Reveal
Twin studies are the most direct way researchers estimate how much genes contribute to a trait. If identical twins (who share 100% of their DNA) are more likely to both experience gender dysphoria than fraternal twins (who share about 50%), that points to a genetic influence. Several studies have tackled this question, and the results vary widely.
One of the most cited findings comes from a study by Heylens and colleagues, which found that 39.1% of identical twin pairs were concordant for gender dysphoria, meaning both twins experienced it, while 0% of fraternal same-sex pairs were concordant. That gap strongly suggests genetic involvement. A study by Diamond, however, found concordance rates of 33% and 23% among fraternal same-sex pairs for people assigned male and female at birth, respectively, which complicates the picture.
Heritability estimates, which capture how much of the variation in a trait can be attributed to genetic differences in a population, range from as low as 11% for adult gender identity to as high as 70% for cross-gender behavior in children. One study estimated heritability of clinically significant gender dysphoria at 62%. Another found it was 50% for people assigned male at birth and 37% for those assigned female. These numbers aren’t contradictory so much as they reflect different populations, different ages, and different ways of defining the trait being measured.
A large register-based population study in Scientific Reports added an unexpected wrinkle. Among 40 same-sex twin pairs where one twin had gender dysphoria, zero co-twins also had it. That means no concordant identical twins were found in that sample. However, 37% of different-sex twin pairs were concordant. The authors noted this could reflect the influence of sharing a prenatal hormonal environment with an opposite-sex twin rather than shared genetics alone.
Specific Genes Linked to Gender Dysphoria
Researchers have moved beyond twin studies to look for specific genetic variants that might increase the likelihood of gender dysphoria. Most of this work has focused on genes involved in how the body produces and responds to sex hormones, since these hormones shape brain development before birth.
The androgen receptor gene has drawn the most attention. This gene contains a repeating DNA sequence (called a CAG repeat) that varies in length between individuals. Longer repeats reduce how effectively the receptor responds to testosterone. A study of 112 transgender women and 258 cisgender men found that transgender women had significantly longer repeat lengths, suggesting their bodies may respond less strongly to testosterone during the critical window of brain development. Less effective testosterone signaling during prenatal life could, in theory, result in a brain that develops along a less typically masculine path.
A broader candidate gene study published in the Journal of Clinical Endocrinology & Metabolism examined several genes involved in sex hormone signaling. Transgender women were more likely to carry certain variants in genes related to estrogen receptor function and an enzyme involved in processing testosterone. Carrying one of these variants increased the likelihood of being transgender by about 1.6 times. The study also identified four two-gene interaction patterns that were overrepresented in transgender women, suggesting that combinations of genetic variants may matter more than any single gene.
For transgender men, a polymorphism in the CYP17 gene has shown an interesting pattern. This gene influences levels of testosterone, progesterone, and estradiol. In a study of 142 transgender men and 168 control women, a specific variant (the A2 allele) was more common in transgender men than in control women. Notably, this allele’s distribution in the general population doesn’t differ between sexes, but among transgender individuals, it was significantly more common in trans men than trans women.
Epigenetics: Beyond the DNA Sequence
Your genes don’t change over your lifetime, but how actively they’re read and used does. Chemical tags attached to DNA, particularly methyl groups, can dial gene activity up or down without altering the genetic code itself. This process, called DNA methylation, is shaped by both your underlying genetics and your environment, including the hormonal environment you experienced in the womb.
Research comparing transgender and cisgender individuals before any hormone therapy has found over 1,200 sites on non-sex chromosomes where DNA methylation patterns differ between people assigned male and female at birth. These patterns are established early in development and are remarkably stable. When transgender individuals begin hormone therapy, only about 3% of sex-specific methylation patterns change, and those tend to be sites that naturally shift during puberty rather than ones set before birth.
A study published in Scientific Reports found that a specific gene called CBLL1 was less methylated in transgender men compared to cisgender women, and this difference correlated with cortical thickness, the physical structure of the brain’s outer layer. Brain imaging studies have consistently found that transgender individuals show cortical thickness patterns and white matter structure that don’t neatly match either cisgender men or cisgender women, sometimes falling in between or resembling their experienced gender rather than their sex assigned at birth. The CBLL1 finding hints that epigenetic changes could be one mechanism connecting genetic variation to these brain differences.
Why No Single “Gender Identity Gene” Exists
The research consistently points to gender dysphoria being influenced by many genes, each with a small effect, interacting with prenatal hormone levels and epigenetic modifications. This is similar to how height, personality traits, or susceptibility to depression works. No single gene variant is necessary or sufficient to produce gender dysphoria. Instead, a combination of genetic variants may create a predisposition that interacts with the hormonal environment during fetal brain development.
The genes identified so far all cluster around sex hormone signaling: how hormones are produced, how they’re metabolized, and how effectively receptors in the brain respond to them. This fits with the longstanding hypothesis that gender identity is shaped, at least in part, by prenatal hormone exposure during a critical period of brain development. Genetic variants that subtly alter this hormonal environment could shift the trajectory of brain sexual differentiation.
The Autism Connection
One of the more striking findings in recent years is the overlap between gender dysphoria and autism spectrum disorder. A meta-analysis pooling data from 25 studies and over 8,600 people with gender dysphoria found that 11% also had an autism diagnosis. That’s roughly 11 times the prevalence of autism in the general population. People with gender dysphoria also scored moderately higher on measures of autistic traits compared to the general population, even when they didn’t meet diagnostic criteria for autism.
The reasons for this overlap aren’t fully understood, but one possibility is shared genetic architecture. Both conditions involve differences in brain development, and some of the same biological pathways, particularly those involving sex hormones and their effects on the developing brain, have been implicated in both. This doesn’t mean gender dysphoria is a form of autism or vice versa, but it suggests that some of the same genetic and prenatal factors may contribute to both.
What the Evidence Adds Up To
Gender dysphoria is partially heritable, with genetics accounting for a meaningful but incomplete share of who develops it. The best evidence points to dozens or possibly hundreds of genetic variants, mostly in hormone-related genes, each nudging the probability slightly. These genetic influences likely operate through their effects on prenatal brain development, modulated by epigenetic processes that determine how actively those genes function during critical developmental windows. No genetic test can predict or diagnose gender dysphoria, and the trait clearly involves substantial non-genetic influences that researchers are still working to identify.