Purpose: In global forensic practice, some suicides were misclassified as undetermined deaths, leading to suicide underreporting. In this study, we aimed to explore the influence of undetermined deaths on suicides in Shanghai, China.
Methods: The police records on suicide verdicts and undetermined deaths in Pudong, Shanghai, from 2004 to 2016 were used. In this study, undetermined deaths have been classified into three levels of suicide possibilities namely, probable, possible, and highly unlikely. Probable suicides were presumed as misclassified suicides. Poisson regression was used to calculate the rate ratio ("RR") of probable suicides compared to suicide verdicts. Poisson regression was also used to calculate the annual percentage change ("APC") of the original suicide rates (crude suicide rates based on the suicide verdicts) and adjusted suicide rates (crude suicide rates based on the suicide verdicts and probable suicides).
Results: Among the 1,318 underdetermine deaths, 560 (42.5%) were classified as probable suicides. The overall RR was 0.23 (95% CI 0.21-0.26): 0.15 (0.13-0.17) for the locals' RR and 0.22 (0.19-0.26) for the migrants' RR. The APCs of the original and adjusted suicide rates were - 2.0 (- 3.1 to - 0.9) and - 2.9 (- 3.8 to - 2.0), respectively, for the overall population.
Conclusions: The number of suicides could be 23% higher than the reported cases. Suicides were more likely to be underreported in migrants than in the locals. Thus, it is important to improve suicide monitoring and the surveillance systems in China.
Keywords: China; Suicide; Underreporting; Undetermined death.