A consideration of the validity and reliability of suicide mortality data.

The question of the validity and reliability of suicide statistics may be considered at three levels: (1) Are suicide deaths misidentified or differentially identified across jurisdictions or over time? (2) To what degree are suicide deaths misidentified? and (3) Is the degree to which suicides are misidentified sufficient to threaten the validity of research based on suicide statistics? There is general agreement that suicides are likely to be undercounted, both for structural reasons (the burden-of-proof issue, the requirement that the coroner or medical examiner suspect the possibility of suicide) and for sociocultural reasons. There is also substantial anecdotal and empirical evidence suggesting that the mode of death for some true suicides is in fact certified as other than suicide. Overall, it does not seem that very many true nonsuicides are incorrectly certified as suicides. There is not, however, much agreement as to the degree to which true suicides are undercounted. At least some of the inconsistencies in the findings of different investigators arise because the validity of suicide certification seems to vary from place to place. But the source of apparent conflicts in many of the findings is undoubtedly the lack of a "gold standard" against which the verdicts of any given death certification process can be measured. At best, we can estimate that the sensitivity with which coroners and medical examiners certify true suicides varies from approximately 55% to 99%. A central question in estimating the sensitivity of suicide certification is this: What proportion of true suicides are either equivocal or likely to go unsuspected by the coroner or medical examiner? Very little has been done to investigate this issue. Yet the sensitivity of suicide certification clearly varies for equivocal versus unequivocal suicides. As shown in Table 1.2, specificity is also at issue when it comes to certifying equivocal cases. The final question--whether the degree of undercounting of suicide deaths is so great that it threatens the validity of research based on official statistics--is at the crux of the general concern about suicide certification. There are examples of studies in which conclusions based on crude comparisons of reported suicide statistics appear to be invalid. For the most part, these are comparisons among nations with substantially differing death certification procedures. When official statistics are interpreted with a degree of caution and an understanding of the source and direction of biases likely to affect the published rates, however, it seems unlikely that major conclusions based on these statistics will be in error.(ABSTRACT TRUNCATED AT 400 WORDS)