Beyond the Sexed-Brain Hypothesis

Daphne Garrido

Preprint 5 · September 2026 - Preprint on Zenodo

The Neurobiology of Gender Incongruence.pdf

Researchers have found measurable brain differences. Understanding what they mean is the real challenge.

A brain scan can make a scientific result look almost self-explanatory.

A colored region appears on an image. Two groups differ. It is tempting to conclude that researchers have discovered the place where the phenomenon “lives.”

Neuroscience is rarely that simple.

MRI can reveal anatomy. Diffusion imaging can estimate properties of white matter. Functional imaging can measure activity-related changes. Other methods can investigate connectivity, blood flow, or neurochemistry.

These technologies can tell scientists that brains differ.

They do not automatically tell scientists why.

That distinction is central to The Neurobiology of Gender Incongruence.

The earliest clues were intriguing—and tiny

Some historically influential research examined small brain structures after death.

Researchers reported characteristics in transgender women that appeared closer to female than male comparison groups.

The observations became important because they suggested that neural characteristics might relate to experienced gender.

But the transgender samples were extremely small.

Participants were adults. Treatment histories varied. The measurements captured brains after decades of development and experience.