Insomnia in medical students during an examination period: associations with depression, dysfunctional sleep beliefs, and academic performance

Background Insomnia is common among medical students and is linked to impaired mental health and academic functioning. Medical students are exposed to persistent psychosocial stress, yet the extent to which state factors (e.g., stress, mood) versus trait factors (e.g., chronotype, sleep beliefs) contribute to insomnia severity is unclear. While dysfunctional sleep beliefs are relatively stable cognitive traits, they remain amenable to targeted interventions. Methods We conducted a cross-sectional survey at a German medical school during a fourth year exam period. Students completed the Insomnia Severity Index (ISI; primary outcome), selected items of the Pittsburgh Sleep Quality Index (PSQI), the Patient Health Questionnaire-9 (PHQ-9), the Generalized Anxiety Disorder-2 (GAD-2), a visual analogue scale (VAS) for stress, the Dysfunctional Beliefs and Attitudes about Sleep Scale-16 (DBAS-16), and reduced the Morningness–Eveningness Questionnaire (rMEQ); academic performance was recorded. Group differences were tested with t tests and chi-square tests. A multivariable linear regression modeled insomnia severity (ISI) as a function of state and trait variables; a secondary model examined DBAS-16 subscales. Results Of 124 students, 46.0% (57/124) screened positive for clinically relevant insomnia symptoms (ISI > 10). Students with clinically relevant inomnias symptoms had shorter total sleep time (391.0 ± 76.5 vs. 438.2 ± 58.3 min; P < 0.001), longer sleep onset latency (51.1 ± 37.1 vs. 21.6 ± 18.0 min; P < 0.001), and lower sleep efficiency (82.2% ± 12.2% vs. 90.1% ± 7.2%; P < 0.001). In adjusted analyses (R² = 0.572; adjusted R² = 0.523), higher PHQ-9 (β = 0.30; P = 0.01) and DBAS-16 (β = 0.28; P < 0.001) were independently associated with higher ISI, whereas higher sleep efficiency (β = −0.30; P < 0.001) and academic performance (β = −0.15; P = 0.037) were inversely associated; perceived stress, anxiety, and chronotype were not independent correlates. In the DBAS-16 subscale model (R² = 0.332; adjusted R² = 0.307), Worry/Helplessness and Perceived Consequences were significantly associated with higher ISI. Conclusions Clinically relevant insomnia symptoms were frequent among medical students. Depressive symptoms and dysfunctional sleep beliefs were key correlates of insomnia severity, and academic performance was inversely related. These findings suggest that sleep health and mental well-being deserve attention in medical education and student health services.