Although the prevalence of drug overdose has gradually increased worldwide, the risk factors associated with the recurrence of suicide attempts via drug overdose have not been well elucidated. In this study, we investigated the clinical course of patients with drug overdose and whether or not patients reattempted suicide via overdose, using telephone interviews, to evaluate the risk factors associated with overdose recurrence.

This prospective observational study enrolled patients who attempted suicide by drug overdose and were transferred to a tertiary emergency hospital in Japan between January 1, 2015 and July 30, 2021. Recurrence of overdose within 1 year of admission for overdose was designated as the primary outcome. Multivariable logistic regression analysis was performed to assess the independent risk factors for the recurrence of overdose. Furthermore, we compared the difference in the recurrence interval between patients with and without cohabitants using the log-rank test.

A total of 94 patients were identified, and recurrence of overdose was observed in 28 patients (29.8%). The median recurrence interval was 6.0 months [IQR (interquartile range), 4.0–7.0 months]. The recurrence rate was significantly higher in patients with a history of schizophrenia than that in patients without a history of schizophrenia (58.3% vs 25.6%, p = 0.048), and significantly lower in patients with cohabitants than that in patients without cohabitants (22.6% vs 43.8%, p = 0.015). The presence of a cohabitant was significantly associated with a longer recurrence interval (p = 0.049). The effect of psychiatric intervention during hospitalization and psychiatric visits after discharge could not be found in this study.

A history of schizophrenia was an independent risk factor for the recurrence of overdose, and the presence of a cohabitant was significantly associated with a lower risk of recurrence. Large-scale, long-term studies are required to confirm the results of this study.