Nonfatal Self-Inflicted Injuries Treated in Hospital Emergency Departments --- United States, 2000

CDC, in collaboration with the Consumer Product Safety Commission (CPSC), expanded CPSC's National Electronic Injury Surveillance System (NEISS) in July 2000 to include all types and external causes of nonfatal injuries treated in U.S. hospital emergency departments (EDs) (1). This ongoing surveillance system, called NEISS All Injury Program (NEISS-AIP), provides data to calculate national estimates for nonfatal injuries treated in EDs during 2000. This report provides national, annualized, weighted estimates of nonfatal self-inflicted injuries treated in U.S. hospital EDs. Overall, self-inflicted injury rates were highest among adolescents and young adults, particularly females. Most (90%) self-inflicted injuries were the result of poisoning or being cut/pierced with a sharp instrument, and 60% were probable suicide attempts. NEISS-AIP data increase understanding of self-inflicted injuries and can serve as a basis for monitoring trends, facilitating additional research, and evaluating intervention approaches.

NEISS-AIP includes data from 66 of the 100 NEISS hospitals, which were selected as a stratified probability sample of all hospitals in the United States and its territories with a minimum of six beds and a 24-hour ED (2,3). The NEISS-AIP hospitals are a nationally representative sample of U.S. hospital EDs. NEISS-AIP provides data on approximately 500,000 injury- and consumer product--related ED cases each year. Data from these cases are weighted by the inverse of the probability of selection to provide national estimates (2). Annualized estimates for this report are based on weighted data for 2,008 nonfatal self-inflicted injuries treated in EDs during July--December 2000. The weight of each case was doubled, and then these weighted values were added to provide annualized estimates for the overall population and population subgroups (i.e., age, sex, and race/ethnicity*). A direct variance estimation procedure was used to calculate 95% confidence intervals and to account for the complex sample design (2).

Injuries were defined as bodily harm resulting from acute exposure to an external force or substance, including unintentional and violence-related causes. Cases were excluded if 1) the principal diagnosis was an illness, pain only, psychological harm (e.g., anxiety and depression) only, contact dermatitis associated with exposure to consumer products (e.g., body lotions, detergents, and diapers) and plants (e.g., poison ivy), or unknown; or 2) the ED visit was for adverse effects of therapeutic drugs or of surgical and medical care (4). Injuries were classified into mutually exclusive categories according to the intent of injury (i.e., unintentional, assault, self-inflicted, and legal intervention^†). This analysis is limited to nonfatal self-inflicted injuries. Data about sex, race/ethnicity, injury mechanism (e.g., fall, struck by/against, and cutting/piercing), and disposition were collected. The mechanism of injury represents the precipitating mechanism that initiated the chain of events leading to the injury, similar to the underlying cause for injury-related death. Mechanisms of injury were classified into recommended major external cause-of-injury groupings (4,5) by using definitions consistent with International Classification of Diseases, Ninth Revision, Clinical Modifications (ICD-9-CM) external-cause coding guidelines (6). To evaluate the likelihood that a nonfatal self-inflicted injury was suicide-related, CDC analyzed verbatim text comments recorded in the NEISS-AIP database from ED patient charts for each injury. A self-inflicted injury was categorized as a probable suicide attempt if the text comments specifically indicated that the injury resulted from an attempt to take one's own life. A self-inflicted injury was deemed a possible attempt if the chart did not explicitly mention suicidal behavior but indicated that the patient had a history of condition(s) associated with suicidal behavior (e.g., depression or a previous suicide attempt). The remaining self-inflicted injuries were categorized as unclear/unknown regarding intent.

During 2000, an estimated 264,108 persons were treated in EDs for nonfatal self-inflicted injuries (rate: 95.9 per 100,000 population) (Table 1); the rate for females (107.7) was higher than that for males (83.6). An estimated 170,222 (65%) injuries resulted from poisonings, 65,256 (25%) were attributed to injuries with a sharp instrument, and 3,016 (1%) involved a firearm (Table 1). The causes of self-inflicted injuries were similar for males and females, although the proportion attributed to poisoning was higher for females (72%) than for males (55%). An estimated 129,832 (49%) persons were treated and released from EDs, 85,287 (32%) required hospitalization, and 41,784 (16%) were transferred to another institution for care. An estimated 158,466 self-inflicted injuries (60%) were considered probable suicide attempts, and 27,294 (10%) were considered possible attempts; for 78,358 self-inflicted injuries (30%), the information in the text field was unclear/unknown regarding intent. By age, rates were highest among adolescents aged 15--19 years and young adults aged 20--24 years (259.0 and 236.6, respectively), with the highest rate occurring among females aged 15--19 years (322.7). By race/ethnicity, rates were highest among white, non-Hispanic males (71.8) and females (93.9).

Reported by: R Ikeda, MD, R Mahendra, MPH, L Saltzman, PhD, A Crosby, MD, L Willis, MA, J Mercy, PhD, Div of Violence Prevention; P Holmgreen, MS, JL Annest, PhD, Office of Statistics and Programming, National Center for Injury Prevention and Control, CDC.

Editorial Note:

The findings in this report highlight the magnitude of nonfatal self-inflicted injuries in the United States and their disproportionate impact on females and young persons. This report supplements previous NEISS-AIP summary results by providing descriptive characteristics of self-inflicted injuries.

A substantial proportion of persons who deliberately harmed themselves might not have intended to die. Further study is required to clarify the relation between self-inflicted injuries and suicidal behavior and to identify the unique characteristics of self-inflicted injuries that are not intended to result in death. Defining the differences or similarities between the various categories of self-inflicted injuries (i.e., those that are suicide-related and those that are not) might have important implications for prevention efforts of these injuries.

The findings in this report are subject to at least three limitations. First, estimates are based on data collected for a 6-month period and might not reflect seasonal differences in the number of self-inflicted injuries. Second, outcomes are specific to ED visits and do not include more distant outcomes (e.g., those resulting from hospitalization or transfer to another facility). Finally, the number of probable suicide attempts might be underestimated. NEISS-AIP data are based only on information contained in ED records and are not linked or supplemented with other data sources (e.g., hospital discharge records or police records). A patient might be unable or unwilling to report a self-inflicted injury initially as suicidal behavior but might do so later, or a health-care provider might not ask specific questions about intent.

The estimate of probable suicides in this report is lower than that in the National Hospital Ambulatory Medical Care Survey (NHAMCS) (7). NEISS-AIP records only the initial ED visit; NHAMCS records both the initial ED visit and any subsequent visits related to a specific injury event. Methods to identify external cause for violent injury (8) and to standardize nomenclature (9) need to be improved.

This analysis highlights the usefulness of NEISS-AIP for estimating the number of self-inflicted injuries treated in U.S. hospital EDs and for providing descriptive information about those injuries. NEISS-AIP data can help public health professionals understand better the magnitude and characteristics of self-inflicted injuries and serve as a basis for monitoring trends, facilitating additional research on the costs and consequences of injuries, and evaluating suicide prevention efforts such as the National Strategy for Suicide Prevention (10).

References

1. CDC. National estimates of nonfatal injuries treated in hospital emergency departments---United States, 2000. MMWR 2001;50:340--6.
2. U.S. Consumer Product Safety Commission. The NEISS sample: design and implementation. In: Kessler E, Schroeder T, eds. Washington, DC: U.S. Consumer Product Safety Commission, 2000.
3. U.S. Consumer Product Safety Commission. NEISS coding manual 2000. Washington, DC: U.S. Consumer Product Safety Commission, 2000.
4. CDC. Recommended framework for presenting injury mortality data. MMWR 1997;46(No. RR-14).
5. CDC. A training module for coding mechanism and intent of injury for the NEISS All Injury Program. In: Annest JL, Pogostin CL, eds. Atlanta, Georgia: U.S. Department of Health and Human Services, CDC, National Center for Injury Prevention and Control, 2000.
6. U.S. Department of Health and Human Services. Generic ICD-9-CM. Hospital version 1999. Reno, Nevada: Channel Publishing LTD, 1998.
7. McCaig LF, Burt CW. National Hospital Ambulatory Medical Care Survey: 1999 Emergency Department Summary. Advance data from vital and health statistics; no. 320. Hyattsville, Maryland: U.S. Department of Health and Human Services, CDC, National Center for Health Statistics, 2001.
8. Institute of Medicine. Reducing the burden of injury: advancing prevention and treatment. Washington, DC: National Academy Press, 1999.
9. O'Carroll PW, Berman AL, Maris RW, Moscicki EK, Tanney BL, Silverman MM. Beyond the Tower of Babel: a nomenclature for suicidology. Suicide Life Threat Behav 1996;26:237--52.
10. U.S. Public Health Service. National strategy for suicide prevention: goals and objectives for action. Washington, DC: U.S. Department of Health and Human Services, 2001.

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