Review: Gender Identity Based in Biology, Not the Mind

By Kait Scalisi, MPH

For decades, transgender individuals have been referred to psychiatric treatment, told it’s all in their heads or it is something they can change. Behind the scenes, however, researchers have been looking for biological underpinnings of gender identity. Now a new study from Boston University has reviewed the existing data and reached one conclusion: there is a strong support for the biological nature of gender identity.

Before discussing the review itself, it is important to make a few notes. First, the available data on the biologic basis of gender identity is neither broad nor deep. It is limited in rigor, sample size, etc. Nevertheless, it is what we have right now and this review provides an important starting point and call to action to further examine the mechanisms of gender identity. It is the first step in educating healthcare providers to not simply refer transgender patients to psychiatry but rather to treat them medically (e.g. hormones, gender affirming surgery, etc).

Secondly, you may be wondering why it matters if we know why someone is transgender and why we can’t just accept people for who they are. This is a valid point, and certainly the hopes of transgender individuals and their allies, but it is also the ideal. Healthcare providers and public health professionals rely on data to inform their work. In addition, transphobic arguments often center around non-binary gender identities as being a choice. Having such data is the first step in ensuring transgender individuals have access to appropriate, informed, and compassionate healthcare.

Now that those potentially contentious points are out of the way, let’s look at the research.

The study looked at studies and examined different potential biologic bases for gender identity issues. These included:

Disorders of sexual development, such as penile agenesis
Neuroanatomical differences, such as in the amount of grey and white matter
Steroid hormone genetics, such as genes associated with sex hormone receptors.

From these three areas the researchers reached three major conclusions:

Abnormal hormone exposure may result in someone being transgender. This is not expected to be the norm as the bulk of transgender individuals have normal sexual differentiation.
There are transgender-specific neuroanatomical differences. Specifically, the sexual differentiation of the brain in transgender individuals differs from that of their physical body. So transmasculine individuals have brain structures that look similar to those of cis-gender men.
Genetic factors including abnormalities associated with steroid hormones, twin case studies, neuroproteins, and prenatal exposures may also lead to a transgender identity.

How does this review help? Physicians continue to be wary of treating transgender patients with surgery and hormones. This is likely due to a combination of personal biases, misunderstanding about trans identities, and a lack of research showing the need for such approaches. The researchers are transparent in sharing that the goal of the subject was to better establish this biological basis so they could then/with the hopes that physicians will then treat patients medically instead of just referring them to therapy. The study also hopes to solves step one—determining whether gender identity is biologic—so researchers can shift their focus to the underlying mechanisms of this biology while healthcare providers focus on how to best address the needs of transgender individuals.

The evidence presented in the article also fights against the idea that gender identity can be changed via psychotherapy/psych treatment. This places the burden of treatment on the medical/healthcare providers. As the study’s PI says:

“If you realize that gender identity, to a large extent, is a biologic phenomenon, then you aren’t going to say, ‘Oh you should just deal with it’ […] You’re going to want to know what is the most logical intervention based on success.”

The authors note that future research should focus on the best interventions and treatment approaches for transgender patients as well s more overall research on the exact biological mechanism by which gender identity and gender identity issues are determined.