New graduate nurses show declining mental health over three years with increased work time and night shifts.

This study aimed to establish a dynamic follow-up cohort of new graduate nurses to systematically explore the dynamic changes and developmental trajectory of their mental health status within 3 years after employment. It further analyzed differences in mental health at different time points and factors associated with these trajectories, with the goal of providing empirical evidence for early identification of psychological risks and implementing targeted psychological interventions. This would assist new graduate nurses in successfully navigating the role transition period. A prospective longitudinal study using a dynamic cohort design was conducted from 2019 to 2024. A total of 130 new graduate nurses were recruited across three cohorts; of these, 118 completed the baseline assessment. Follow-up assessments were completed by 115 (97.5% of baseline) at year one, 115 (97.5%) at year two, and 102 (86.4%) at year three. Overall, 88 participants (74.6% of those with baseline data) completed all four assessments. A self-designed general information questionnaire and the Symptom Checklist-90 (SCL-90) were used to assess mental health status across 10 dimensions. A linear mixed-effects model was employed to examine longitudinal trends and factors associated with mental health trajectories. Time was modeled as a continuous variable (coded as 0, 1, 2, 3) to estimate longitudinal associations. Over the 3-year period after employment, the mental health status of new graduate nurses showed a gradual decline as their working time increased. Among the symptoms, obsessive-compulsive states were the most prominent. The linear mixed-effects model revealed statistically significant differences (P < 0.05) in scores across seven dimensions: somatization, depression, anxiety, fear, hostility, psychoticism, and eating/sleep problems. Further analysis indicated that new graduate nurses who fell asleep quickly with better sleep quality, worked no night shifts, and held the title of “nurse” had significantly better mental health than those who experienced difficulty falling asleep with poor sleep quality, worked night shifts, and held the title of “senior nurse” (β = 11.62; β = −7.72; β = 7.23; β = 12.12). This longitudinal study finds that while new graduate nurses' overall mental health remains acceptable within 3 years, it declines significantly with experience. The trajectory evolves in stages: a “high-pressure role adaptation phase,” a “plateau phase of adaptation decline,” and a “career development confusion phase,” with issues especially in somatization, anxiety, and depression. Key associated factors include sleep quality, time to fall asleep, night-shift frequency, and professional title. Nursing managers should monitor these dynamic changes and implement early interventions—such as better sleep management, optimized scheduling, and phased psychological support—to facilitate successful role adaptation.