From acute presentation to post-discharge outcomes: intentional Z-drug versus benzodiazepine overdose in a retrospective cohort

Background Z-drugs are alternatives to benzodiazepines (BZDs) for insomnia, but overdose safety remains uncertain. We compared acute and post-discharge outcomes after intentional Z-drug and BZD overdose. Methods This retrospective cohort included 239 adults (110 Z-drug; 129 BZD) treated at two emergency departments without flumazenil (2018–2024). Models adjusted for age, sex, dose category, intent, and center. Results Compared with BZD overdose, Z-drug overdose was associated with more recorded physical restraint use (adjusted odds ratio [aOR], 6.974; 95% confidence interval [CI], 3.358–14.483), more recorded patient-behavior-related medical interruption events (PB-MIEs; aOR, 5.955; 95% CI, 2.732–12.980), and a longer emergency-department stay (adjusted median difference, 2.516 h; 95% CI, 2.056–2.845), but fewer intensive care unit (ICU) admissions (aOR, 0.092; 95% CI, 0.031–0.272). Among admitted patients, total stay was longer after Z-drug overdose (228 vs 146 h, P < 0.001). The hazard of a first documented anxiety and/or depressive diagnosis was higher after Z-drug overdose (adjusted hazard ratio [aHR], 2.918; 95% CI, 1.928–4.416). Recurrence proportions were similar (25.5% vs 23.3%; log-rank P = 0.426), but timing differed. The recurrence Cox model violated the proportional-hazards assumption; the adjusted HR of 1.266 is descriptive, not a constant relative risk. Among 58 recurrent cases, standard single-dose (SSD) multiples declined and documented intent shifted toward sleep-related dose escalation; this pattern may partly reflect assessment or documentation differences. Conclusion Z-drug overdose was associated with more recorded behavioral-management events and a higher hazard of first documented psychiatric diagnosis, whereas BZD overdose was associated with more severe supportive-care outcomes. Initial care should integrate mental-status and respiratory monitoring with behavioral and self-harm assessment. Follow-up should address insomnia, medication safety, and mental health. Recurrence timing and intent shifts were documented associations, not causal effects.