UNIversity students' LIFEstyle behaviours and Mental health cohort (UNILIFE-M): study protocol of a multicentre, prospective cohort study.

The UNILIFE-M study is designed to enroll participants from 69 universities across 28 countries, with 300 participants targeted per site.

• Participants will be recruited from 69 universities in 28 countries.
• Target enrollment is 300 participants per site.
• Participants will be assessed at university admission in the 2023 and/or 2024 academic year.
• The study uses an online survey platform for self-reported data collection.

The study follows a prospective cohort design with four assessment time points spanning 3.5 years.

• Baseline assessment occurs at university admission.
• Follow-up assessments are planned at 1, 2, and 3.5 years after baseline.
• The longitudinal design allows tracking of changes in lifestyle behaviours and mental health symptoms during college years.
• The study uses self-reported data gathered through an online survey.

The study assesses seven categories of mental health symptoms across participants.

• Mental health outcomes include depression, anxiety, mania, sleep problems, and substance abuse.
• Additional mental health outcomes include inattention/hyperactivity and obsessive/compulsive thoughts/behaviours.
• The inclusion of multiple mental health symptom categories addresses a limitation of prior research that focused on a limited set of outcomes.
• All mental health data are self-reported.

The study assesses eight categories of lifestyle behaviours as exposures of interest.

• Lifestyle behaviour domains include diet, physical activity, substance use, and stress management.
• Additional domains include social support, restorative sleep, environment, and sedentary behaviour.
• This multi-domain approach addresses the limitation of prior research that focused on single lifestyle behaviours.
• All lifestyle data are self-reported via online survey.

The study received initial ethics approval at a national level in Brazil, with additional institutional ethics approvals obtained by sites outside Brazil.

• The study was first approved in Brazil with ethics certificate number CAE:63025822.8.1001.5346.
• Study sites outside Brazil obtained additional ethics approval from their own institutions.
• The main Brazilian approval served as the basis for international site approvals.

The UNILIFE-M study was motivated by identified gaps in existing research on university student mental health.

• Prior research is described as limited by focusing on single lifestyle behaviours.
• Existing studies are characterized as including single time points, limiting longitudinal understanding.
• Prior research is noted to be conducted within limited cultural contexts.
• Students enrolling in higher education often adopt lifestyles linked to worse mental health, contributing to the peak age onset of mental health problems in early adulthood.

Results from the UNILIFE-M cohort will be disseminated through multiple channels.

• Planned dissemination channels include scientific publications and presentations at scientific meetings.
• Additional dissemination will occur through press releases, general media, and social media.
• No results data are presented in this protocol paper.