Introduction
The transition to university represents a significant period of adaptation for students. This study aimed to assess lifestyle patterns among first-year undergraduate students and to examine their associations with sociodemographic, academic, and mental health factors during the first academic semester. 

Methods
We conducted a prospective closed-cohort study with first-year undergraduate students from a Brazilian public university. At baseline (T1), 288 students completed an online survey, and 140 were reassessed at the end of the semester (T2). Lifestyle was assessed using the University Short Multidimensional Inventory on Lifestyle Evaluation (U-SMILE), and depressive and anxiety symptoms were measured using the Patient Health Questionnaire (PHQ-9) and the Generalized Anxiety Disorder-7 (GAD-7). We used linear regression models to examine cross-sectional associations at baseline and repeated-measures ANCOVA to examine changes in lifestyle according to depression and anxiety screening trajectories.

Results
At baseline, male students, higher family income, and enrollment in health-related programs were associated with higher lifestyle scores. Lower substance use, better sleep, greater social support, and higher total lifestyle scores were associated with fewer depressive and anxiety symptoms scores. Lifestyle scores did not change across the semester, yet higher scores were observed among students with persistently negative screening for depression or anxiety.

Conclusion
Lifestyle behaviors did not change during the first academic semester. Still, better lifestyle scores were associated with healthier mental health among first-year university students. These findings suggest that differences in lifestyle and mental health may reflect baseline characteristics rather than short-term changes during the semester.