Trade Queer

I’ve been tagged in this a lot today, so here goes: Before we can talk meaningfully about transgender neurology, we first need to understand what the literature says about sex differences in the brain more generally. There are documented sex differences (on average) across various domains including white matter microstructure, cortical thickness, grey matter volume, and both structural and functional connectivity. These differences have been observed in both human and animal studies. However, it’s critical to understand that these differences stem from a combination of biological and methodological factors. Some are simply due to the overall larger brain volume typically seen in males (which affects certain metrics more than others), while others may reflect social influences or even sexual orientation. Some identified differences maybe age-dependent, while others might not arise until there is damaging pathology. Regardless of the source, these differences are generally small when examined in isolation (i.e., univariate analyses), and the specific brain regions showing sex-related differences can vary from study to study, often due to differing methodological designs. Importantly, there’s no clear-cut dichotomy here, only general trends, some of which are more consistent than others. Now, turning to the data on transgender individuals: the so-called “brain-sex hypothesis” is the most frequently cited framework. But the quality of the existing data is, frankly, not great. Many studies include transgender participants who are already on cross-sex hormone therapy (sometimes for years!) or who also identify as homosexual. Why does this matter? Because both hormone therapy and sexual orientation are independently known to influence brain structure and function, and, crucially, they’re associated with the same kinds of “cross-sex shifts” that researchers are trying to study. We have direct evidence showing that each of these variables can alter the brain in ways that mimic sex-related patterns. In fact, when researchers have scanned the brains of heterosexual transgender individuals who have NOT undergone cross-sex hormone therapy, their brains tend to resemble those of their natal sex. Bottom line: correlation is not causation.

🖕🏻 For all transphobic people.