4.3.3 - Gender incongruence

Meaning and boundaries

AQA's updated Gender topic uses the term gender incongruence. The key idea is a persistent mismatch between a person's experienced gender and the sex they were assigned at birth. This lesson is about explanations for that mismatch. It is not a general lesson on all gender identities, and it is not asking students to treat gender diversity as abnormal.

The distinction matters. A person can have a gender identity that differs from their assigned sex without wanting medical transition, without identifying within a binary category, and without experiencing the same level of distress as another person. The updated AQA wording helps separate incongruence from the older, more pathologising language of "atypical gender development" and "gender identity disorder".

Clinical classifications add requirements beyond a short classroom definition, so a scenario exercise is not a diagnosis. Preferences for clothes, play or activities alone do not establish gender incongruence. The ICD-11 classification is useful background. It moved gender incongruence out of the mental and behavioural disorders chapter and into a sexual health chapter. The logic is that trans and gender-diverse identities are not mental illnesses, but a classification may still help some people access healthcare and support.

Prevalence is difficult to estimate because studies measure different things: clinical diagnoses, referrals to services, identity survey responses, or distress. For exam purposes, do not turn prevalence into a causal claim. The specification requires biological and social/cultural explanations: a social explanation or a cultural explanation is acceptable; both are not compulsory. The studies and examples below are routes to developing an explanation, not a list that every answer must reproduce.

AO1: define gender incongruence accurately and distinguish it from identity, expression and dysphoria.

AO2: in scenarios, look for the mismatch between experienced gender and assigned sex, not simply a preference for clothes, toys or activities.

AO3: keep the language socially sensitive. Avoid saying that gender incongruence is a "choice", a "disorder" or a simple result of parenting, peers or media.

Genes and prenatal hormones

Biological explanations argue that gender incongruence may be influenced by inherited factors, prenatal hormones or the way the body responds to hormones during development. These explanations are usually probabilistic, not deterministic: they suggest increased likelihood, not inevitability.

Genetic influence. Twin studies are useful because monozygotic twins share nearly all of their DNA, whereas dizygotic twins share about half of their segregating genes. Heylens et al. (2012) reviewed twin case reports where at least one twin had what older sources called gender identity disorder. They reported 9 concordant pairs out of 23 monozygotic twin pairs, about 39.1%, compared with no concordant pairs among 21 same-sex dizygotic twin pairs. This is consistent with a genetic contribution because concordance was higher in genetically identical twins. It does not isolate inheritance from shared environments or the greater similarity of treatment that monozygotic twins may experience.

The evaluation is just as important as the finding. Monozygotic concordance was not 100%, so the result does not support a simple rule that an identical genotype guarantees an identical outcome. This does not by itself identify which environmental or developmental processes account for differences. The review also depended on case reports and older diagnostic categories, so it is less strong than a large population-based twin study would be.

Candidate genes and androgen sensitivity. Hare et al. (2009) compared DNA from 112 transgender women with 258 cisgender male controls. They focused on genes linked to sex-steroid pathways and found an association with longer CAG repeat length in the androgen receptor gene. Longer repeats can reduce the effectiveness of androgen signalling, so the study was interpreted as evidence that androgen response may be involved in some cases of gender incongruence.

This is a useful AO1 study, but do not overclaim it. A candidate-gene association does not mean there is a single "gender incongruence gene". The study did not measure prenatal brain development directly, and an association in selected groups needs replication before it supports a robust developmental account. It also focused on transgender women, so it cannot automatically explain transgender men, non-binary people or all forms of gender incongruence.

Prenatal hormones. Hormone explanations focus on the organisation of the brain and body before birth. Androgens such as testosterone help shape some sex-linked physical characteristics and may also influence later gendered interests or identity.

Two examples often used in AQA teaching are CAH and AIS:

AO2 example. A researcher finds that a biological marker is more common in a group of transgender participants than in a matched cisgender control group. The safest interpretation is that the marker may be associated with gender incongruence. It would be too strong to say the marker "causes" gender incongruence unless the study design can establish cause and effect.

Brain sex theory

Brain sex theory proposes a developmental contribution: some sex-linked neural characteristics may correspond more closely to experienced gender than to assigned sex. “Brain sex theory” is a historical explanatory label, not evidence that brains fall into two uniform types. An early research focus was the central subdivision of the bed nucleus of the stria terminalis (BSTc).

Zhou et al. (1995) examined post-mortem brain tissue from six transgender women. They reported a female-typical BSTc volume in this small group compared with their control groups. This was a measurement of one region, not the sex or gender of an entire brain. The authors argued that this supported the idea that gender identity may develop through an interaction between the brain and sex hormones.

Kruijver et al. (2000) followed a similar post-mortem approach and found that the number of somatostatin-expressing BSTc neurons in transgender women was also female-typical relative to their controls. This strengthened the biological explanation because it was not just a difference in volume; a second measure of the same brain region pointed in a similar direction.

More recent imaging work has looked at wider brain patterns. For example, Rametti and colleagues used diffusion tensor imaging with participants before cross-sex hormone treatment. Some findings suggested white-matter patterns closer to experienced gender, though results were not simple enough to claim that there is a single male brain and a single female brain.

AO3 strength: converging evidence. Brain studies provide biological evidence from post-mortem examination and neuroimaging. The fact that different methods have reported sex-linked differences relevant to gender identity makes the biological explanation more credible than a purely speculative account.

AO3 limitation: small and selective samples. Zhou et al. and Kruijver et al. used very small samples, and post-mortem research is difficult to replicate with large, representative groups. Many studies also use binary categories and older terminology, so the evidence may not generalise well to all gender-diverse people.

AO3 limitation: cause and effect. Even if brain differences are found, it is difficult to know whether they cause gender incongruence, result from hormone treatment or life experience, or are correlates rather than causes. The original post-mortem authors considered adult hormone histories and argued that treatment did not explain their findings; those comparisons remain limited by small numbers and incomplete control of life histories. Studies before hormone treatment reduce that particular alternative, but do not show the neural pattern preceded experienced identity or exclude learning and other developmental influences.

AO3 limitation: reductionism. Brain sex theory can be useful, but it risks oversimplifying gender identity into a single brain region. Modern Psychology should avoid implying that a person needs a particular scan result for their identity to be valid.