3D Follow-up Study

Transition Study: Challenges and resources of children and families in the transition from preschool to grade school in a pregnancy cohort

Since the beginning of the 3D study, many follow-up have been carried out to assess specific aspects of child development. Two of those follow-up are done by the DePSA lab: 3D-Transition and 3D-Transition-Ado.

The 3D-Transition follow-up (2017-2022) studies 939 participants from the 3D pregnancy cohort  as they transitioned to kindergarten and first grade. It aimed to examine the developmental mechanisms linking children’s early resources and challenges to mental health after the transition to formal schooling. Biannual assessments included questionnaires administered to both parents as well as teachers, observations of parent-child interactions, anthropometric measurements (e.g., height, weight), and age-sensitive cognitive assessments. Saliva sample from a subsample of 384 participants were also collected on 11 days over a 16-month period to examine possible changes in salivary cortisol levels across the school transition, and the role that these cortisol levels may have played in the difficulties observed during the transition. A combination of planned missing data designs are implemented to reduce participant burden, where incomplete data are collected without introducing bias after the use of multiple imputation.

The 3D-Transition study will contribute to an evidence-based developmental framework of children mental health from the womb to school age. In turn, this framework can help inform prevention programs delivered in health care settings during pregnancy, childcare centers, preschools, and schools.


This project is funded by the Canadian Institute of Health Research (CIHR) and is led by a team of researchers from the Université de Montréal, the Université de Sherbrooke, the Université Laval and the CHU Sainte-Justine Research Center: Séguin, Jean R. – Université de Montréal; Parent, Sophie  -Université de Montréal; Archambault, Isabelle -Université de Montréal; Boivin, Michel – Université Laval; Castellanos-Ryan, Natalie – Université de Montréal; Fraser, William – Université de Sherbrooke; Herba, Catherine – Université du Québec A Montréal; Lupien, Sonia – Université de Montréal; Marc, Isabelle- Université Laval; Muckle, Gina – Université Laval


The 3D-Transition-Ado follow up

With the goal to continue studying developmental transitions, the 3D-Transition-Ado follow-up (2023-2029) has been added to the 3D-Transition study. It follows 608 participants from the 3D birth cohort as children transition to puberty and through adolescence.

Once a year, participating parents and children are invited to fill an online questionnaire that includes a variety of measures on mental health, puberty, social life, environment, sex/gender and other key-factors of the transition to puberty and adolescence. Hair samples are collected every year to examine possible changes in children’s hair cortisol levels across puberty and adolescence.

Through this work, the 3D-Transition-Ado follow-up will contribute to understand the role of puberty on developmental trajectory of mental health among children and adolescents. This follow-up aims to study not only pubertal development as such, but also how puberty interacts with early childhood characteristics and the psychosocial environment (family, peers, school experience) throughout development during adolescence.

Researchers: Castellanos-Ryan, Natalie – Université de Montréal; Séguin, Jean R. – Université de Montréal; Parent, Sophie  -Université de Montréal; Boivin, Michel – Université Laval; Herba, Catherine – Université du Québec A Montréal; Juster, Robert-Paul- Université de Montréal.