ABSTRACT The suicide rates officially reported by most countries are widely believed to be lower than actual rates, attributable partly to inaccuracy of registration of deaths and misclassification of cause of death. In this review paper, we discuss under-counting of deaths and of suicides, referring to findings from international research. We then describe the three main ICD-10 cause of death categories that possibly harbour 'hidden suicides': ill-defined or unknown causes of death, events of undetermined intent (EUI), and accidental deaths. We used the 2017 Australian mortality statistics to illustrate these three categories. The World Health Organization (WHO) data and international research show (1) that mortality data provided to the WHO by a large number of its Member States are of questionable quality and not timely; and (2) substantial variations among countries in rates of suicide, ill-defined or unknown deaths, EUIs, and accidental deaths (notably, poisoning). Accurate reporting of suicides is needed to advance research on suicide prevention and develop more effective suicide prevention programmes. Nations should endeavor to obtain, publish and analyse data regarding annual rates of deaths coded as of ill-defined/unknown cause, EUI, and accidental poisoning and other relevant types of accident.
Keywords: accidental deaths; events of undetermined intent; ill-defined or unknown causes of death; suicide; underreporting.