Aim. To assess physical activity, sleep quality, and the mental health status of students during wartime, to explore their interrelationships, and to examine the mediating role of sleep quality.

Materials and methods. A cross-sectional study was conducted among 245 first- to third-year students of State Non-Profit Enterprise “Danylo Halytsky Lviv National Medical University”aged 18–24 years (mean age 19.15 ± 0.95 years; 25 % males, 75 % females). Validated Ukrainian versions of standardized instruments were used: Perceived Stress Scale-14 (PSS-14, stress), Hospital Anxiety and Depression Scale (HADS, anxiety and depressive symptoms), Pittsburgh Sleep Quality Index (PSQI, sleep quality), and International Physical Activity Questionnaire – Long Form (IPAQ-LF, physical activity). Statistical analysis included descriptive statistics, Student’s t-test, one-way ANOVA, χ2 test, Pearson’s correlation, and mediation analysis (Hayes’ PROCESS Macro, model 4, with 5000 bootstrap resamples).

Results. Most students reported moderate stress scores (74.3 %). Elevated anxiety levels (HADS) were found in 38.8 % of participants, while increased depressive symptoms were observed in 7.3 %. Sleep disturbances (PSQI >5) were found in 64.1 % of students, with the most affected components being daytime dysfunction, sleep latency, and dissatisfaction with sleep quality. A high level of physical activity was observed in 73.9 % of students. Sleep quality showed a strong correlation with depressive symptoms (r = 0.473, p < 0.001), a moderate correlation with anxiety (r = 0.373, p < 0.001), and a weak correlation with stress scores (r = 0.230, p < 0.001). Physical activity was not directly associated with stress or anxiety but was significantly correlated with better sleep quality (r = -0.253, p < 0.001). Mediation analysis demonstrated that the effect of physical activity on depressive symptoms (β = -0.120; 95 % CI: -0.177 to -0.062) and anxiety (β = -0.097; 95 % CI: -0.147 to -0.050) was fully mediated by sleep quality, whereas for stress only partial mediation was observed (β = -0.059; 95 % CI: -0.106 to -0.020).

Conclusions. Students during wartime exhibited a high prevalence of mental health issues combined with frequent sleep disturbances. Despite a generally high level of physical activity, sleep quality emerged as the key predictor and mediator of stress, anxiety, and depressive symptoms. These findings highlight the need for integrated programs that address both physical activity and sleep hygiene to safeguard students’ mental health in wartime conditions.