This is a fascinating study of identical twins; one had gender dysphoria and one did not. Both twins developed anorexia.
Both twins were feminine in behavior from a young age and both were sexually attracted to men. Both had a difficult childhood with an abusive father.
Both twins were underweight at birth and needed intensive care. Both had developmental delays.
However, one twin considered himself to be a gay man while one identified as a straight woman.
In this case study, gender dysphoria did not cause the eating disorder.
This case highlights the importance of other factors in eating disorders, including genes, hormones, and trauma.
It raises the question; how important is gender identity as a cause of eating disorders?
This case is different from other case studies where gender dysphoria seems to be intimately linked to the eating disorder.
We can’t look at these two patients and conclude that gender dysphoria never contributes to eating disorders. However, this case is a good reminder to be cautious about drawing conclusions from other case studies. Perhaps there are just some people with eating disorders who also have gender dysphoria. Or perhaps there is some other factor which causes both eating disorders and gender dysphoria.
As always, we need more studies.
More about the Patients:
Twin A was diagnosed with AN-purging subtype and Twin B was diagnosed with AN-restricting subtype.
Twin B developed an eating disorder at an earlier age, but Twin A was more underweight and had a more disturbed perception of his body. Furthermore, Twin A was hospitalized for his eating disorder and Twin B was not.
Neither twin seems to have been able to maintain a healthy weight.
At age 16 Twin A “was admitted to a children’s hospital because of AN. Later, he was hospitalized in the psychiatric inpatient unit for adolescents. At first, his eating behavior was restrictive. Then he reported intermittent vomiting (AN binge-purge). His weight decreased to 46 kg/1.79 m (body mass index [BMI] ¼ 14.3 kg/m²). His ideal weight was 44 kg according to a BMI of 13.7 kg/m² , which shows his severe disturbance in body perception. During hospitalization, his behavior was sometimes aggressive. He was emotionally unstable, depressed, and was rarely able to engage in stable relationships. Despite strict dietary rules, he achieved a maximal weight of 55 kg (BMI ¼ 17.2 kg/m²). Soon after being discharged, his weight decreased again.”
Twin B’s eating disorder began at a younger age. “In puberty, he developed severe underweight. At the age of 13, he was 42 kg/1.58 m (BMI ¼ 16.8 kg/m² ). When he was referred to our outpatient unit at the age of 18½ years [for gender dysphoria], his weight was 48 kg and his height was 1.76 m (BMI ¼ 15.5 kg/m² ). He denied deliberate dieting, binging, or purging. Although he regarded himself as too slim, he did not manage to gain weight. Further medical checkups revealed no somatic cause for his underweight. An osteodensitometry yielded an osteopenia of the spine.”
Twin A was a gender non-conforming gay male:
“In childhood, he preferred girls’ games and toys (Barbie dolls) and was very close to his twin brother. His sexual feelings were always for males. Although he started cross-dressing at the age of about 16 years, his gender identification was always male. He considered himself to be a homosexual.”
Twin B was a trans woman:
“As far as he could remember, he had felt he was a girl, preferring girls as playmates and had started cross-dressing at nursery school. In gymnastic lessons, he refused to change with the other boys because he was ashamed of his body. Eventually, he refused to attend sports lessons at all. When he was 9 years old, he started to grow his hair. His class mates seemed to accept him as a girl. When he started to work as a hairdresser, he tried to correspond to the male gender role and did not cross-dress. However, at his professional school and in his free time, he continued to cross-dress. His employer, who realized he was transsexual, permitted and encouraged him to cross-dress at work, which consequently allowed him to live as a young woman. Sexually, he was always attracted to men. However, in contrast to his brother, he never considered himself to be homosexual and viewed this attraction as ‘‘heterosexual.’’ Until this point, he had not engaged in sexual relationships either with men or with women.”
Twin B requested hormonal and surgical sex reassignment.
The twins grew up together in a small Swiss city without any other siblings. Their childhood was not easy:
“[Their father] was very authoritarian. He could not accept the sexual orientation and the cross-dressing of his sons and threatened them with assault and even with death.
…In family conflicts, [their mother] took a position between her husband and her sons. At a family consultation, she appeared emotionally unstable.”
The birth was a difficult one. Both twins were underweight and spent time in intensive care.
“the mother had been admitted to a hospital with hypertension, edema, and proteinuria at 38 weeks of gestation. The vaginal delivery was induced because of maternal preeclampsia. Twin A weighed 2.17 kg at delivery and his Apgar score was 9/9/9. Because of perinatal acidosis and hypotonia, he was kept in the incubator for 3 days. He was diagnosed with a subependymal hemorrhage with ventricular invasion. Twin B’s birth weight at delivery was 1.95 kg and his Apgar score was 7/9/9. Both twins were admitted immediately to the neonatal intensive care unit.”
They both had developmental delays:
“In early childhood, Twin A showed a developmental delay in language and motor skills and had deficits in cognitive and verbal skills. He was socially isolated and his behavior was often aggressive.”
“…Twin B had delays in language and motor development during early childhood. He showed the typical symptoms of attention deficit and hyperactivity disorder. The parents refused further assessment and treatment.”
Twin A was diagnosed with borderline personality disorder and subnormal verbal intelligence.
Twin B was diagnosed with gender dysphoria.
There is no obvious pattern to any of this. Twin A was larger at birth, but had more problems right after birth. Both had developmental delays, and Twin B may have had ADHD as well. Both were feminine in their behavior, but only Twin B developed gender dysphoria. Both were sexually attracted to men. Twin B developed an eating disorder earlier, but Twin A’s eating disorder seems more severe. Twin A has borderline personality disorder and Twin B does not.
The authors offer two possible hypotheses about the twins’ gender identity.
Perhaps the twins are on a continuum of gender non-conformity where gender dysphoria is at the extreme end.
Alternatively, perhaps gender dysphoria* in childhood is inherited, but the later development of gender identity is determined by environmental factors and psychiatric comorbidity.
“In childhood, both Twin A and Twin B showed gender atypical behavior and stereotypical feminine traits and interests. In adolescence, their sexual orientation was revealed to be homosexual. Twin A developed effeminate homosexuality with male gender identity, whereas Twin B stabilized his cross-gender identity. Although Twins A and B are concordant for GID in childhood and sexual orientation on a categorical level, they are now discordant for TS. On a more dimensional level, one could argue that Twins A and B show an opposite sex-dimorphic behavior and that they arrived at different points of a continuum. The fact that GID in childhood is a predictor for later homosexuality and TS could support the dimensional view. It could be hypothesized that GID in childhood is mainly hereditary, whereas the development of the later phenotype of the gender identification is determined by environmental factors and psychiatric comorbidity, as any difference between MZ twins provides strong evidence for the role of environmental influences.”
The authors also discuss the relationship between gender and eating disorders. However, they don’t address the fact that the two twins had different gender identities, but both had eating disorders.
Perhaps both gay men and trans women are vulnerable to eating disorders for different reasons, but perhaps genes, hormones, and environment matter more than gender identity.
“Homosexual men seem to have an increased vulnerability to eating disturbance and body dissatisfaction (Williamson & Hartley, 1998), are more dissatisfied with their weight (French, Story, Remafedi, Resnick, & Blum, 1996), and are more concerned about their attractiveness (Siever, 1994). Male AN is associated with disturbed psychosexual and gender identity development, which supports the hypothesis that males with atypical gender role behavior have an increased risk of developing an ED (Fichter & Daser, 1987). Furthermore, feminine gender traits are discussed as a specific risk factor for ED in men and women (Meyer, Blissett, & Oldfield, 2001). Although the role of sexual orientation as a risk factor for ED is well documented, there is hardly any literature about GID and ED. For men with disturbance of gender identity in addition to the aforementioned factors concerning sexual orientation, underweight could be a way to suppress their libido and the expression of their secondary sexual characteristics and, at the same time, correspond to a female ideal of attractiveness (Hepp & Milos, 2002).”
We need more research!
“Further research in eating behavior and body dissatisfaction in patients with GID could provide more insight into the role of gender identity in the development of ED and lead to a better understanding of ED as well as GID.”
* In this case, gender non-conformity might be a more fitting phrase. Twin A does not seem to have ever wanted to be a girl.
Gender Identity Disorder and Anorexia Nervosa in Male Monozygotic Twins by Urs Hepp, Gabriella Milos, and Hellmuth Braun-Scharm in Int J Eat Disord. 2004 Mar;35(2):239-43.