# The interplay between gender identity and sex assigned at birth in adolescents’ health and wellbeing: a cross-sectional study

## TL;DR

This study explores how gender identity and sex assigned at birth affect adolescent health and wellbeing in Catalonia, showing that transgender and gender expansive youth face worse health outcomes than cisgender peers.

## Contribution

The study highlights the importance of considering both gender identity and sex assigned at birth in health research, rather than using one to replace the other.

## Key findings

- TGE AMAB adolescents had worse overall health and mental wellbeing compared to cisgender boys.
- TGE AFAB adolescents had worse overall health than cisgender girls, though mental discomfort was not significantly different.
- Interpersonal relations and health behaviors partially explain the differences in health outcomes among groups.

## Abstract

There is a growing body of evidence on health inequalities according to gender identity, in which sex assigned at birth is often overlooked. The aim of our study was to assess the relevance of examining both gender identity and sex assigned at birth in health population surveys, by comparing the health outcomes, behaviours, and interpersonal relationships in cisgender boys, cisgender girls, transgender and gender expansive (TGE) youth assigned male at birth (AMAB) and TGE youth assigned female at birth (AFAB), in a general population sample of adolescents schooled in Catalonia, Spain.

Cross-sectional study using a questionnaire in students aged 12–19 years from Catalonia (N = 9177) in 2021–2022. We assessed the differences in health outcomes (self-perceived overall health and mental wellbeing), health-related behaviours (quality of diet, physical activity, consumption of tobacco, alcohol and cannabis, and compulsive screen and digital entertainment use), and interpersonal relationships (family relationships, bullying victimization, and sexual violence) in cisgender boys, cisgender girls, TGE AMAB and TGE AFAB, using descriptive statistics and Pearson chi-square tests. We used Poisson regression models with robust variance to examine the associations between the health outcomes and gender identity and sex assigned at birth.

TGE AMAB adolescents had a greater prevalence of worse overall health (PRadj=2.01, 95% CI: 1.14–3.52) and mental discomfort (PRadj=1.63, 95% CI: 1.20–2.23) than cisgender boys. TGE AFAB adolescents had an increased prevalence of worse overall health (PRadj=1.81, 95% CI: 1.42–2.31) than cisgender girls, while the association with mental discomfort was not statistically significant (PRadj=1.13, 95% CI: 0.97–1.31). TGE AFAB had an increased prevalence of worse overall health (PRadj=1.95, 95% CI: 1.07–3.53) and mental discomfort (PRadj=1.47, 95% CI: 1.05–2.05) than TGE AMAB adolescents. Interpersonal relations and health-related behaviours partly explained these associations.

TGE adolescents have worse health outcomes than cisgender peers and, simultaneously, adolescents who were AFAB (cisgender girls and TGE AFAB) have worse health outcomes than those AMAB (cisgender boys and TGE AMAB, respectively). In health research, gender identity should complement, not substitute, sex assigned at birth.

The online version contains supplementary material available at 10.1186/s12889-025-25954-5.