Study on the Impact of Affirmative Medical Care in Transgender Adolescents - Pediatric Research Foundation
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The PARLONSMAAT Project: A Longitudinal Participatory Cohort Study on the Impact of Affirmative Medical Care in Transgender Adolescents

An estimated 0.5% of Quebec adolescents (2,500 aged 12-17) identify as transgender and non-binary, meaning that their internal gender identity does not match their biological sex. Many of them will begin the process of gender affirmation (transition) during adolescence.

Although gender-affirming medical care, such as puberty blockers, hormones and surgery, started to be available to transgender adolescents at specialized gender diversity clinics in the early 2000s, very few studies have described their impact on the physical health, mental health, well-being and quality of life of these adolescents.

Existing research has generally studied small groups of adolescents over short periods, limiting the ability to fully understand the actual effects of the treatments received. In addition, treatment recommendations are evolving rapidly, and existing studies do not reflect current medical practice.

The gender diversity clinic at the Sainte-Justine University Hospital Centre is the first interdisciplinary clinic in Quebec to offer free medical care and psychosocial support to transgender and non-binary children and adolescents aged 8 to 18. It combines the expertise of clinicians in adolescent medicine, pediatric endocrinology, general pediatrics, child psychiatry, gynecology, social work, nursing and psychology, and collaborates closely with professionals in the healthcare network, including partners at several Quebec hospitals. The clinic is also involved in numerous research projects with researchers at the Université de Montréal and other centres of expertise in the rest of Canada and around the world.

It is well known that transgender youth present mental health problems, such as depression, anxiety, eating disorders and suicidal ideation at rates that are 2 to 3 times higher than for the general population. Transgender youth are also diagnosed with autism spectrum disorders 4 to 5 times more frequently than youth in the general population. In the short term, gender-affirming treatments have the potential to reduce mental health problems experienced by transgender adolescents to levels similar to those seen in cisgender adolescents (for whom gender identity matches biological sex). However, the long-term effects of gender-affirming treatments on health and well-being remain unknown, given the novelty of this approach in adolescents.

There is therefore an urgent need for longitudinal cohort studies, i.e. studies that follow large groups of adolescents over a long period to better understand how they progress following treatment.


Given the large number of transgender children and adolescents in Canada (10,000 teens aged 12 to 17, according to the latest survey and census data), the PARLONSMAAT project will identify the tangible impacts of gender-affirming care and determine how best to support transgender adolescents to promote their health, well-being and development.

We anticipate recruiting 200 to 400 participants during the initial 3-year phase of the project, a number that could rise to over 1,000 if the project continues for an additional 5 years.

Thus, our study will create a vast database that will enable us to track the evolution of the care received and the long-term outcomes of the participants, as well as validate best medical practices for the support of transgender adolescents.


The PARLONSMAAT project aims to respond to a pressing need to study the tangible effects of gender-affirming treatments on the health and well-being of transgender adolescents.

The specific objectives of the project will be to study the following 4 elements related to gender-affirming care in pediatrics :

  • The effects of puberty blockers and gender-affirming hormones (e.g. testosterone and estrogen) on the physical and mental health of transgender adolescents
  • The impact of family and peer support on the mental health and well-being of transgender adolescents
  • Differences in care needs and trajectories between male and female transgender adolescents
  • The impact of different demographic factors (e.g. spoken language, ethnicity, socioeconomic status) and developmental factors (e.g. autism spectrum disorder) on the care trajectories of transgender adolescents


This project will lead to the creation of the largest research cohort of transgender adolescents in North America, and the only one of its kind in Quebec.

The unique research design using a participatory approach in close collaboration with transgender adolescents and their families will enable a quality of data not found in other existing studies, and will further interpretation of results to better improve the care offered to this population.


At least 4 students will be trained directly by this project. One master’s student will participate in the project for 2 years, supervised by the principal investigator.

Three pre- or post-graduate students will also carry out summer internships under the supervision of the research team. Given the impressive amount of data to be collected, several pre- and post-doctoral students will also be joining the research team.


The funding received will enable the PARLONSMAAT cohort to establish itself as a pillar of transgender adolescent health research in North America.

Initially conducted at a single centre (CHU Sainte-Justine), the study may be extended to other partner sites (e.g. CHU de Québec, CHU de Sherbrooke) that are currently developing their own gender diversity clinics.

The funding will also give the project the credibility it needs to obtain major research grants to ensure its sustainability.


Principal researcher

  • Dr Nicholas Chadi, pédiatre et chercheur spécialisé en médecine de l’adolescence diplômé des universités McGill, de Montréal, de Toronto et Harvard.


  • Annie Pullen-Sansfaçon PhD – Université de Montréal
  • Diane Rottembourg MD – CHU de Sherbrooke
  • Kevin Lavoie PhD – Université Laval
  • Laurence Arsenault-Blanchard MD – CHU de Québec
  • Lyne Chiniara MD MA – CHU Sainte-Justine

Research Center

  • Centre de recherche du CHU Sainte-Justine

Funded year


Project category

  • Neurodevelopment and mental health