Validity and reliability of trends in suicide statistics

Abstract

For a number of reasons, suicide is under-reported and the reliability of official rates is subject to error through variations in defining and reporting cases, the kind of inaccuracy encountered when ascertaining cases in studies of mortality from any cause. Nevertheless, the evidence from studies designed to see whether these sources of error invalidate the differences reported between cultural and social groups indicates that they are of a random nature, at least to an extent that allows epidemiologists to compare rates between countries and districts within them, between demographic groups, and over periods of time. The accuracy and hence the value of official suicide statistics has been questioned in recent years to an extent that has led some authorities to dismiss their usefulness in epidemiological research. In England and Wales, a decision as to whether an unexpected or violent death is a suicide or not is normally made at a coroner's inquest; similar, but by no means identical procedures are followed in other developed countries. Cases defined and ascertained in this way are the usual source of national suicide statistics. Indeed, it may be claimed that the medical and post-mortem inquiry together with the evidence of witnesses on the psychological and social circumstances relating to the act, entail a more thorough investigation into this cause of death than is usual in compiling the statistics of deaths from other causes. Consider by contrast the General Registrar Office enquiry into the accuracy of reporting other causes of death (1). When, for example, deaths from cancer of the lung are registered before holding a post-mortem and the cause of death is later checked by a pathologist, the net error is about 16%. The conclusions drawn from official cancer statistics, however, are not seriously questioned. It is thus reasonable to expect suicide statistics, despite inaccuracies, also to be of heuristic value particularly as over-reporting is negligible, and it is only under-reporting, not a matter in dispute, that need be considered. Studies of under-reporting of suicide include those done in England and Wales (2), Scotland (3), and in Ireland where McCarthy & Walsh (4) examined coroners' case records in Dublin using clinical criteria to assess the probability of suicide. Though their revised rate was considerably higher than the official one, the Irish rate is still exceptionally low when compared with other countries. Barraclough (5) confirmed by other means that the adjusted rate was still half that of England.(ABSTRACT TRUNCATED AT 400 WORDS)