Introduction The number of adolescents referred to specialized gender identity clinics for gender dysphoria appears to be increasing and there also appears to be a corresponding shift in the sex ratio, from one favoring natal males to one favoring natal females. Aim We conducted two quantitative studies to ascertain whether there has been a recent inversion of the sex ratio of adolescents referred for gender dysphoria. Methods The sex ratio of adolescents from two specialized gender identity clinics was examined as a function of two cohort periods (2006–2013 vs. prior years). Study 1 was conducted on patients from a clinic in Toronto, and Study 2 was conducted on patients from a clinic in Amsterdam. Results Across both clinics, the total sample size was 748. In both clinics, there was a significant change in the sex ratio of referred adolescents between the two cohort periods: between 2006 and 2013, the sex ratio favored natal females, but in the prior years, the sex ratio favored natal males. In Study 1 from Toronto, there was no corresponding change in the sex ratio of 6,592 adolescents referred for other clinical problems. Conclusions Sociological and sociocultural explanations are offered to account for this recent inversion in the sex ratio of adolescents with gender dysphoria.

This study is the third in a series to examine behavioral and emotional problems in children and adolescents with gender dysphoria in a comparative analysis between two clinics in Toronto, Ontario, Canada and Amsterdam, the Netherlands. In the present study, we report Child Behavior Checklist (CBCL) and Youth Self-Report (YSR) data on adolescents assessed in the Toronto clinic (n = 177) and the Amsterdam clinic (n = 139). On the CBCL and the YSR, we found that the percentage of adolescents with clinical range behavioral and emotional problems was higher when compared to the non-referred standardization samples but similar to the referred adolescents. On both the CBCL and the YSR, the Toronto adolescents had a significantly higher Total Problem score than the Amsterdam adolescents. Like our earlier studies of CBCL data of children and Teacher’s Report Form data of children and adolescents, a measure of poor peer relations was the strongest predictor of CBCL and YSR behavioral and emotional problems in gender dysphoric adolescents.

In Western cultures, male androphiles tend to have greater numbers of older brothers than male gynephiles (i.e., the fraternal birth order effect). In the non-Western nation of Independent Samoa, androphilic males (known locally as fa'afafine) have been shown to have greater numbers of older brothers, older sisters, and younger brothers (Vasey & VanderLaan, 2007). It is unclear, however, whether the observed older brother effect, in the context of the additional sibling category effects, represented a genuine fraternal birth order effect or was simply associated with elevated maternal fecundity. To differentiate between these two possibilities, this study employed a larger, independent replication sample of fa'afafine and gynephilic males from Independent Samoa. Fa'afafine had greater numbers of older brothers and sisters. The replication sample and the sample from Vasey and VanderLaan were then combined, facilitating a comparison that showed the older brother effect was significantly greater in magnitude than the older sister effect. These results suggest that fraternal birth order and maternal fecundity effects both exist in Samoa. The existence of these effects cross-culturally is discussed in the context of biological theories for the development of male androphilia.

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