Objective The aim of this study was to investigate the associations between shift work (including night work) and multiple prescriptions of anxiolytic and antidepressant drugs (PAD) among nursing staff in Region Stockholm, Stockholm County’s healthcare authority.

Methods Using register-based data, 32 375 nurses and nursing assistants employed at Region Stockholm for ≥1 year between 2008 and 2019 were included. Exposures were obtained from an employee register, while PAD were obtained from a national pharmaceutical register. With a one-year follow-up, discrete-time proportional hazards models were used to estimate hazard ratios (HR) after adjusting for covariates, in a final analytical sample of 17 834.

Results Increased hazards of PAD were recorded among those who were on permanent night shifts [HR 1.39, 95% confidence interval (CI) 1.32–1.47] compared to those who worked days only. We observed a dose–response association between the number of night shifts and PAD. Among night workers, increased hazards were observed for those who worked ≥3 consecutive nights >21 times (HR 1.11, 95% CI 1.03–1.20) compared with those with none. Lastly, among non-night workers, decreased hazards were observed for quick returns from afternoon shifts (<11 hours) compared with those with no quick returns.

Conclusion Exclusive night work is associated with increased risks of multiple PAD compared to day work, implying an increase in risk of mental disorders among nurses and nurse assistants.

Key terms antidepressant; anxiolytic; healthcare worker; night work; observational study; prescription drug; prospective cohort study; Region Stockholm; shift work; shift worker