A 2002 Institute of Medicine report inferred that suicide etiology and prevention in the United States are complicated by undercounting [31
]. Our study yields circumstantial evidence that the official decline in suicide rates between 1987 and 2000 may have been a partial artifact of misclassification within unintentional poisoning mortality. The effect of any such misclassification under poisoning of undetermined intent appeared minimal owing to its very low rates. This study generates additional circumstantial evidence that any underestimation of poisoning suicide, which occurred between 1987 and 2006, primarily involved decedents under age 65 years.
We previously documented that alcohol and other substance abuse can complicate suicide case ascertainment [20
]. A statewide hospital emergency department study estimated that 27% of patients aged 18 years and older needed substance abuse treatment, where need was assessed by means of self-report and validatory toxicological testing [32
]. However, patients aged 65 years and older were only 10-20 percent as likely as younger patients to need such treatment. These comparative findings for hospital emergency department patients, a patently high-risk population [33
], strengthen our conclusion that potential poisoning-associated suicide misclassification is least problematic for the elderly. On the other hand, younger decedents appear much more likely than older counterparts to undergo toxicological testing, as we infer from their far higher national autopsy rates [34
]. However, indirect evidence indicates that medicolegal authorities exercise more caution in ruling or diagnosing suicide among younger than older decedents [18
There are numerous social contributors to suicide underreporting in general and specific underreporting of poisoning suicide. A New York City report in the 1980 s indicated that scarce resources and personnel and policy changes influenced medical examiners to classify many suicides as unintentional injury deaths [12
], a possible artifactual contributor to the contemporaneous and precipitous decline in the suicide rate. While we cannot identify the independent contributions of underfunding of cause-of-death investigations, changing policy, or the prevailing epidemic of unintentional poisoning deaths, our findings indicate that such forces collectively impede suicide case ascertainment, probably explain some of the data trends, and may indirectly foster unwarranted complacency about the suicide burden.
Case ascertainment and rate changes for suicide in the United States can be compared unfavorably to homicide and fatal unintentional motor vehicle traffic trauma. Suicide is more susceptible to underenumeration than these other leading causes of injury mortality because of social pressure and marked contrasts in resources for the affected agencies from medical examiners and coroners to the police, judiciary, and various public and private ancillary organizations. For example, indicating greater fastidiousness in homicide versus suicide investigations, a federal report showed that 92% of homicides in 2003 were autopsied versus 55% of suicides, 77% of undetermined intent deaths, and 73% of unintentional poisoning deaths [34
]. Mean annual age-adjusted death rates for 1987-1989 and 2004-2006, based on the US 2000 standard population, show declines of 28% for homicide and 22% for fatal motor vehicular traffic trauma [28
]. By contrast, the suicide rate decreased 13% and the unintentional poisoning mortality rate increased 233%. Corresponding changes for poisoning of undetermined intent and poisoning suicide were a 102% rise and a 21% decline. At 8 per 100,000, mean crude and age-adjusted unintentional poisoning mortality rates surpassed corresponding homicide rates by one-third in the 2004-2006 triennium. Given the great magnitude and substantial growth of poisoning deaths, we recommend that their investigations be appropriately resourced so that decedent intentionality can be comprehensively assessed together with type and dose of toxin.
Our inferential data, in concert with our justified concern about potential adverse implications for suicide misclassification from stressed resources, challenge the official record that poisoning became a less common method of suicide during an epidemic of unintentional poisoning mortality and era of unprecedented consumer access to a growing pharmacy of potentially lethal toxins [35
]. Access to lethal methods, including prescription drugs, affects suicide rates [36
]. Documenting a sharp rise in fatal poisonings between 1999 and 2006, a new federal government report showed a marked increase in the proportion involving opioid analgesics relative to illicit drugs like heroin and cocaine [37
]. Methadone was the leading cause of death among the opioids, but other significant killers included oxycodone and hydrocodone. There was also a high prevalence of concomitant dual or multiple drug use. Related to physician prescription of stronger analgesics for pain management, the increase in opioid deaths coincided with increased sales for each drug type, including methadone [38
]. Moreover, the increase in methadone deaths has been more closely associated with pharmaceutical sales than with activity in narcotics treatment programs. Media reporting might also be implicated in the epidemic of opioid mortality [39
], and prescription drug diversion is becoming a core issue [38
]. While demographic data lack drug specificity, the largest increase in the poisoning mortality rate occurred at ages 50-59 years, followed by ages 15-29 years [5
]. Distinguishing gender, the highest rate increases were registered for females ages 50-59, followed by females ages 20-29 and males ages 15-19 and 50-59, respectively. Together with measurement or estimation of dosage, identification of specific drugs and combinations of drugs is crucial for developing effective prevention strategies. Deficits in this information likely adversely impact medicolegal assessment of intentionality.
Complicating evaluation of decedent intent, and etiologic understanding of suicide, are the competing beneficial and harmful exposures which characterize the rapid rise of psychotropic medication [41
]. With controversial benefit for youth and the youngest adults, prescribed use of SSRIs alone, for example, seems neutral on suicidal behavior and protects against suicidal ideation in adults ages 25-64 [42
]. This use diminishes the risk of both suicidality and suicidal behavior in those aged 65 years and older. Consideration of our results, in conjunction with those from systematic reviews of antidepressants and suicide risk [43
], leads us to recommend a gender- and age-specific evaluation of the association between psychopharmacology and the decline in elderly suicide rates in particular. It would be prudent for such a study to factor in autopsy rates [45
], since they vary with age [34
This exploratory research possesses a number of limitations. We only indirectly addressed our question concerning the independence of observed trends in suicide and unintentional poisoning mortality rates. Analysis was confined to population-level, underlying cause-of-death data based on death certificates. In precluding poisoning comorbidity, these data underestimate the role of toxic substances in injury mortality, irrespective of manner of death. Moreover, there is no national medical examiner and coroner database that would permit us to analyze and examine the evidence that medicolegal authorities compile and utilize to ascertain suicide. In addition, suicide typically occurs in a local context, whose heterogeneous constellation of determinants includes geography, climate, living and working conditions, access to means of suicide, community attitudes towards suicide and cooperation with death investigators, as well as psychiatric, familial, religious, cultural, and employment variables, race/ethnicity, lifestyles and risk behaviors, and other decedent characteristics.
We think unlikely, but acknowledge in light of our research limitations, that observed trends in national suicide and unintentional poisoning mortality rates could be independent. The clear trend in overall poisoning mortality lends weight to a new argument that suicide prevention must address the gamut of risky behaviors inducing self-destruction beyond those clearly implicating deliberate intent [26
], and another that the definition of suicide needs broadening [47
]. Interviews with survivors of near fatal "unintentional" overdoses documented an ambivalent attitude towards potential death at time of overdose [48
]. Such a finding implied a life-threatening or suicidal component in their self-poisoning. Suicide may be a failed or failing category for classifying and preventing self-harm in the United States [50
], owing to presumed difficulties confronting many medicolegal authorities in evaluating intent during soaring caseloads from the burgeoning poisoning epidemic. Prescription and nonprescription drugs comprise the vanguard of substances with high potential for lethality and abuse. Our results reinforce an identified need for the National Violent Death Reporting System to incorporate unintentional poisonings and other unintentional injury deaths which implicate self-harm, irrespective of decedent intent [26