Fiora Sunshine's post, Why I Transitioned: A Case Study (the OP) articulates a valuable theory for why some MtFs transition.

If you are MtF and feel the post describes you, I believe you.

However, many statements from the post are wrong or overly broad.

My claims:

1. There is evidence of a biological basis for trans identity. Twin studies are a good way to see this.
    
2. Fiora claims that trans people's apparent lack of introspective clarity may be evidence of deception. But trans people are incentivized not to attempt to share accurate answers to "why do you really want to transition?". This is the Trans Double Bind.
    
3. I am a counterexample to Fiora's theory. I was an adolescent social outcast weeb but did not transition. I spent 14 years actualizing as a man, then transitioned at 31 only after becoming crippled by dysphoria. My example shows that Fiora's phenotype can co-occur with or mask medically significant dysphoria.

A. Biologically Transgender

In the OP, Fiora presents the "body-map theory" under the umbrella of "arcane neuro-psychological phenomena", and then dismisses medical theories because the body-map theory doesn't fit her friend group.

The body-map theory is a straw man for biological causation because there are significant sex differences between men and women that are (a) not learned and (b) not reducible to subconscious expectations about one's anatomy.

The easiest way to see this is CAH. To quote from Berenbaum and Beltz, 2021^[1]:

Studies of females with congenital adrenal hyperplasia (CAH) show how prenatal androgens affect behavior across the life span, with large effects on gendered activity interests and engagement, moderate effects on spatial abilities, and relatively small (or no) effects on gender identity

The sex difference in people-vs-things interests (hobbies, occupations) has been discussed extensively in our community. CAH shifts females towards male-patterned interests with small effects on gender identity, without changes in anatomy.

This finding is also notable because it shows male-patterned interests and female gender identity can coexist, at least in natal females.

Twin Studies à la LLM

I'm trans so I have a motive to search for evidence that suggests I am ~biologically valid~ and not subject to some kind of psychosocial delusion. It would be easy for me to cherry-pick individual papers to support that view. I'm trying to not do that. I'm also not going to attempt a full literature review here. Luckily it is 2026, and we have a better option.

The ACE model from psychiatric genetics is a standard framework for decomposing the variance in a trait into 3 components:

A = Additive Genetics: cumulative effect of individual alleles

C = Common Environment: parents, schooling, SES, etc.

E = Nonshared Environment (+ error): randomness, idiosyncratic life events^[2]

There are at least 9^[3] primary twin studies on transgender identity or gender dysphoria. I created an LLM prompt^[4] asking for a literature review with the goal of extracting signal, not just from the trans twin literature, but from other research that could help give us some plausible bounds on the strength of biological and social causation. Here are the results. The format is POINT_ESTIMATE, RANGE:

I'm moderately confident my prompt was not biased because the A values here are lower than what I've gotten from Claude when asking for heritability estimates from twin studies only. Also, all the models included some discussion of the rapid rise in adolescent cases in the 2010s, often mentioning "social contagion" and ROGD theories explicitly. All the models also pointed out that the ACE model is a simplification and that gene-environment interaction may be significant.

These are pretty wide error bars. But since A is trying to capture heredity only, we can take A as a rough lower bound for biological causation. Even if E is purely social, 38% is significant.

Also, none of this tells us how much variation there is at the individual level. And we have no trans GWAS.

The big question is whether E is dominated by social or biological factors.

If social factors mattered a lot I would expect parental attitudes to be significant in affecting transgender identity. But most studies find low C. This holds even for population-based studies that do not suffer from ascertainment bias. I would be surprised if peer influences were highly causal but parental influences were not.

I think the evidence from CAH, fraternal birth order effects, and animal models also provides good mechanistic reasons to think there are significant biological effects in E as well as A.

How do trans people view this line of research? They tend to hate it. They're afraid it will eventually lead to:

1. not choosing "trans embryos" during IVF
2. aborting "trans fetuses"
3. lab/genetic testing to determine who is allowed to medically transition

This is what I'll call "medical eradication": one half of the Double Bind.

B. The Trans Double Bind

The purpose of medicine is to improve health and reduce suffering.

In general, the state should not subsidize healthcare that does not increase QALYs. A rational healthcare system would ration care based on ranking all available treatments by QALYs saved per dollar, and funding all treatments above a cutoff determined by the budget.

The US healthcare system has a very creative interpretation of reality, but other countries like the UK at least attempt to do this.

To receive gender-affirming treatment, trans people must argue that such treatment alleviates suffering. This argument helped establish gender medicine in the 20th century. 

But in fact, the claim "being transgender involves suffering and requires medical treatment" is very controversial within the trans community. This is surprising, because disputing this claim threatens to undermine access to trans healthcare.

Moreover, this controversy explains why trans people do not appear to accurately report their own motivations for transition.

Motivations to transition

There are three possible sources:

1. biological
2. psychological/cognitive
3. social

These can co-occur and interact.

Society at large recognizes only (1) as legitimate.

Trans people know this. They know they may be sent to psychotherapy, denied HRT, or judged illegitimate if they report wanting to transition for psychosocial reasons.

There is strong pressure for trans people to accept and endorse a biological/medical framing for their transitions.

But adopting this framing carries downsides:

• Dependence on medical authorities for legitimacy
  • Historically, medicine has treated us very poorly^[5]
  • We have little power to negotiate for better medical care if we are dependent on medicine to validate us to the rest of society
• Psychological costs
  • Trans-cultural memory of medical mistreatment
  • Many find medicalization demeaning and resent dependence
• Possible medical eradication
  • We can't claim we need care if we don't suffer^[6], but one day the medical system might find a more direct way to eliminate our suffering: preventing trans people from coming into existence in the first place.
     

This is the Double Bind: many trans people need medical treatment, but find the psychological threat of medicalization and eradication intolerable.

Consequently, they will not claim their transition is justified because of biology. However, they know that psychological and social justifications will also not be accepted. In this situation, platitudes like "I am a woman because I identify as one" are a predictable response to incentives. If you attempt to give a real answer, it will be used against you.

Maybe you are thinking:

Marisa, this is hogwash! All the trans people I know are constantly oversharing lurid personal details despite obvious social incentives not to. The most parsimonious explanation is that people who say "I'm __ because I identify as  __" literally believe that.

Yes, good point. I need to explain another dynamic.

So far I've only discussed external incentives, but there is incentive pressure from within the trans community as well.

In the 2010s, the following happened:

• Youth transitions increased
• Nonbinary identification increased, especially among people not medically transitioning 
• Acceptance, awareness, and politicization all increased
• Social media happened

Suddenly the trans community was fighting for a much broader set of constituents and demands. 20th century binary transsexualism coheres with medical framings, but 2010s Tumblr xenogenders do not. And trans people of all kinds have always had insecurities about their own validity-- both internal and external.

Here is the key insight:

It's difficult to enforce norms that protect external political perception.

It's easy to enforce norms that protect ingroup feelings.

Assume I've performed and posted some porn on the internet. This porn is optically really really bad. Like actually politically damaging. Conscientious trans people will attempt to punish my defection-- but this is difficult. I can cry "respectability politics!" and point to the history of trans sex work in the face of employment discrimination. No one can agree on a theory of change for politics, so it's hard to prove harm. When the political backlash hits, it affects everyone equally^[7]. 

By contrast, assume instead that I'm in a trans community space and I've told someone their reasons for transition are not valid, and they should reconsider. I've just seriously hurt someone's feelings, totally killed the vibe, and I'll probably be asked to leave-- maybe shunned long-term^[8]. I have just lost access to perhaps my only source of ingroup social support. This is a huge disincentive. 

This structure, combined with the influx of novel identities in the 2010s, created an environment where it was taboo even to talk about causal theories for one's own transition, because it could be invalidating to someone else. All gender identities were valid at all times. Downstream effects of external social pressure, social media, and politics created an environment of collective ignorance where community norms discouraged investigating the causes of transition.

Introspective Clarity

Famously, trans people tend not to have great introspective clarity into their own motivations for transition. Intuitively, they tend to be quite aware of what they do and don't like about inhabiting their chosen bodies and gender roles. But when it comes to explaining the origins and intensity of those preferences, they almost universally to come up short. I've even seen several smart, thoughtful trans people, such as Natalie Wynn, making statements to the effect that it's impossible to develop a satisfying theory of aberrant gender identities. (She may have been exaggerating for effect, but it was clear she'd given up on solving the puzzle herself.)

This is the wrong interpretation of Natalie Wynn's oeuvre. See Appendix: Contra Fiora on Contra for why.

What would a legitimate explanation of the origins of one's gendered feelings look like?

Fiora never tells us her criteria. And the only example she gives us-- a psychosocial explanation of her own transition-- heavily implies that it was illegitimate.

But she's also dismissive of biological theories. Does that mean no transitions are valid?

I got whole genome sequencing last year. I can point at the sexual and endocrine abnormalities in my genome, but I certainly can't prove they justify my transition. Nevertheless, subjectively, HRT saved my life.

C. In the Case of Quinoa Marisa

(Extremely simplified for brevity)

In middle school, puberty started and my life fell apart. I hated my erections, my libido; I felt like a demon had taken over my brain. Unlike my peers, I never developed a felt sense of how to throw my body around. They got rougher, and better at sports. I got injured.

I was pathologically shy and awkward. Locker room talk was utterly repulsive to me. I lost friends and didn't care. Rurouni Kenshin was my first inspiration to grow my hair out. I am very lucky my parents let me.

There was an autistic kid on my soccer team with a speech impediment. He was good at soccer but the other boys would cruelly tease him at practice, in part because he didn't understand they were teasing him. One night after practice I spent the car ride home sobbing about it in front of my dad, who didn't get it at all. I quit soccer.

I was utterly miserable in school. In March of 7th grade, I developed real depression, and started thinking about suicide. Mom took me to two different psychologists. We decided I would homeschool 8th grade. Now, I really had no friends. I was still depressed.

At this point I was only living for WoW and anime. By far, my favorite was Haibane Renmei. It's 13 episodes of angel-girls living in a run-down boarding school and basically just taking care of each other. It is heavily implied that the Haibane are there-- in purgatory-- because they committed suicide in the real world, and must learn how to accept love and care.

It's difficult to explain how much this series resonated with me. It gave structure to feelings I couldn't articulate. I never believed there was any possibility of becoming a girl in real life, so I didn't fantasize much about that. But for a couple years I daydreamed frequently about dying and becoming a Haibane^[9].

My hair was long enough at this point that I "passed". I was frequently assumed female in social situations, and men would often tell me I was in the wrong bathroom. I longed for delicate reciprocal care with others who somehow understood what I was going through, even though I could hardly understand it myself. Haibane Renmei showed me this but I had no idea how to find it in the real world.

At 16, boy puberty hit me like a truck. I became ugly. I still had no social skills, and no friends. I dressed like a hobo. The summer after junior year I confronted myself in the mirror and admitted I would never be cute again. I still desperately wanted to be loved, and I believed that the only path to achieving that was becoming a man girls would want to date. That meant improving my appearance and social skills.

I knew that women find weebs unattractive. And my long hair was definitely unattractive. It all melded together. I had no real-world outlet for my femininity so I'd poured it all into identifying with anime characters. And it all seemed like a dead end. I felt that if I stayed in the anime community I would end up socially stunted, since its social standards were lower. I cut my hair and stopped watching anime. I put a lot more effort into socializing.

In college, I read The Man Who Would Be Queen, self-diagnosed as AGP, and actually considered transition for the first time. But it was too late for me-- the sight of my face in the mirror, and the depictions of AGPs in the book were too horrifying. I resolved to never transition, and attempted suicide soon after.

7 months later I fell in love, and that relationship turned my life around. I loved her immeasurably for 5 years, and we lived together for 2 of those. I became, on the outside, socially and professionally actualized as a man. I was a great boyfriend and had no problem getting dates. After the breakup I fell in love 2 more times.

You already know how this ends. No amount of true love or social validation as a man could fix me. I never wanted to transition, but at 31 the strain of repression became unbearable. Things have turned out far better than I ever dared imagine. My parents have remarked on multiple occasions, unprompted, how much happier I am now. They're right.

Overall I fit Fiora's phenotype: I was a mentally ill social outcast weeb, desperately identifying with anime characters as a simulacrum of loving care I had no idea how to find in real life.

But I can't explain my eventual transition at 31 through anything other than a biological cause. I looked obsessively for evidence of some repressed or unconscious ulterior motive, and found none. I believed that transition would be very expensive and time-consuming, physically painful^[10], reduce my attractiveness as a mate, and change my social possibilities. All of these predictions have born true. What I didn't expect is that HRT drastically improved my mental health even before the physical changes kicked in. My baseline now is my former 90th-percentile of calm and happiness. 

I'm n=1 but this shows Fiora's phenotype can coexist with biologically rooted dysphoria. Moreover, I believe my middle school social failures were caused as much by gender incongruence as by neurodivergence. It's difficult to socialize when your puberty feels wrong and your social instincts don't match your assigned gender.

It's almost like most of them had deep emotional wounds, often stemming from social rejection, and had transitioned to become cute girls or endearing women as a kind of questionably adaptive coping mechanism.

Maybe. Or a misaligned subconscious sex is part of what caused the social rejection in the first place.

Conclusion

As Fiora implied, "cuteness-maxxing" is probably not a good reason to transition.

Most people desperately want to be loved and this can cause mistakes with transition in both directions. Social media is probably bad for minors. We should emphasize that, at a fundamental level, trans people are neither more nor less lovable than cis people.

The human brain is perhaps the most complex object in our known universe, and we will likely never be able to fully disentangle psychosocial factors from biological ones. That said, I do think humanity will discover ever stronger evidence for biological causes of trans identity within our lifetimes.

Introspection is a noisy way to attempt to answer "am I trans?", and you hit diminishing returns fast. It's also the wrong question. The right question is "should I transition?". Transition is best understood as a Bayesian process where you take small behavioral steps^[11] and update on whether your quality of life is improving.

If you start transitioning and your intrinsic health and happiness improves, and you expect the same to be true in the long run, continue. If not, desist. There is no shame in either outcome.

1. ^{^}

   https://pmc.ncbi.nlm.nih.gov/articles/PMC9186536/

2. ^{^}

   For twins, prenatal environment shows up in both C and E.

3. ^{^}

   Coolidge et al. (2002), Heylens et al. (2012), Karamanis et al. (2022), Conabere et al. (2025), Sasaki et al. (2016), Bailey et al. (2000), Burri et al. (2011), Diamond (2013), Buhrich et al. (1991).

   If you just want to read a systematic review of these studies, see https://pmc.ncbi.nlm.nih.gov/articles/PMC12494644/

4. ^{^}

   I'm trying to understand the etiology of transgender identity, particularly the strength of the evidence base for different categories of potential causes. Please segment the analysis into five categories:

   1. Hereditary/genetic factors
   2. Prenatal environment (hormonal, epigenetic, maternal)
   3. Postnatal biological environment (diet, medications, endocrine factors)
   4. Family/microsocial environment
   5. Macrosocial/cultural environment

   For each category, conduct a rigorous literature review prioritizing meta-analyses, large-N studies, and methodologically sound designs. Identify the strongest evidence both supporting and contradicting causal contributions from that category. Flag studies with clear methodological limitations and discuss known publication biases in the field.

   Focus primarily on gender dysphoria and transgender identity as defined in DSM-5/ICD-11, noting where studies conflate distinct constructs or onset patterns.

   Conclude with a variance decomposition estimate using the ACE framework and liability threshold model standard in psychiatric genetics. Provide:

   - Point estimates with plausible ranges for each component (A, C, E)
   - Confidence ratings for each estimate based on evidence quantity and quality
   - Explicit discussion of what each ACE component likely captures, mapped back to the five categories above
   - Acknowledgment of confounds and unmeasurable factors

   Include cross-cultural and temporal trend data as evidence bearing on the cultural/environmental components.

5. ^{^}

   In general, in the US in the 20th century, if a medical institution decided they simply didn't want to treat trans patients, there would be no public outcry. The doctors and organizations that did treat us could set terms. Prior to the 2010s there was little awareness of trans people, and the awareness we had was often prejudicial. IBM fired Lynn Conway after all.

6. ^{^}

   Some trans people (for example, Abigail Thorn and Andrea Long Chu) have attempted to argue that access to gender-affirming care should not be contingent on either (a) suffering prior to receiving treatment or (b) demonstrated therapeutic benefit for the treatment. These arguments were not well-received even within the trans community.

7. ^{^}

   It took r/MtF until 2025 to ban porn, after years of infighting. https://www.reddit.com/r/MtF/comments/1kaxn18/alright_lets_talk_about_porn_and_porn_accounts/

8. ^{^}

   This norm is not totally unreasonable. The purpose of community spaces is primarily social support for those early in transition, which can be difficult to find anywhere else. I went through this phase too.

9. ^{^}

   Yes, this is perverse and contradicts the moral of the story.

10. ^{^}

    Electrolysis is the most physically painful thing I've experienced. I've done 40 hours so far and will likely do 150-200 total.

11. ^{^}

    Voice training, experimenting with name/pronouns/clothing, laser hair removal, HRT.