University adaptation among first-year medical students: development and psychometric validation of the medical student adaptation questionnaire in Vietnam

University students, particularly in their first year of medical training, face psychological and academic challenges that may impair well-being, hinder performance, and increase dropout risk. Adaptation is essential for meeting academic demands and achieving social integration. This study aimed to identify and validate latent adaptation factors and examine their relationship with medical school adjustment among first-year medical students in Vietnam. A cross-sectional study was conducted among first-year medical students at one of the major medical universities in southern Vietnam. The Medical Student Adaptation Questionnaire (MSAQ) and the College Adjustment Test (CAT) were administered. Test–retest reliability were assessed using intraclass correlation coefficient. Construct validity was evaluated using exploratory and confirmatory factor analyses. Composite reliability, convergent validity, and discriminant validity were examined in the confirmatory phase. Multivariable linear regression with robust standard errors was applied to evaluate the associations between CAT scores and latent factors derived from exploratory factor analysis (EFA) and validated by confirmatory factor analysis (CFA). Among the analyzed first-year medical students (mean age 19.2 years, 50.5% female), the MSAQ demonstrated good reliability, with test–retest reliability indicating excellent stability (ICC = 0.93, 95% CI: 0.88–0.96, p < 0.001). EFA and CFA identified and validated four latent factors, including (1) emotional distress and stress adaptation; (2) self-regulated learning and academic adaptation; (3) peer integration and social belonging; and (4) institutional and academic support environment, explaining 61.0% of the total variance. CFA supported a 17-item structure with acceptable overall fit (CFI = 0.997, TLI = 0.996, RMSEA = 0.053), strong standardized loadings (0.683–0.935), and satisfactory convergent and discriminant validity (CR = 0.80–0.93, AVE = 0.566–0.723, HTMT < 0.85). In multivariable linear regression, all four factors were significantly associated with the CAT scores (p < 0.05), with emotional distress and stress adaptation showing the strongest effect (β = 9.0, 95% CI: 7.9–10.0, p < 0.001). Female students consistently had lower adaptation scores, and students living away from family reported significantly lower adaptation levels than those living with family. This study identified four key domains influencing first-year medical students’ adaptation, with emotional distress and stress adaptation as predominant factors, alongside significant effects of sex and living arrangements. These findings highlight the need for targeted support strategies, structured mentorship, and resilience-promoting policies to enhance student well-being and academic success.