Department of Psychiatry, College of Medicine, National Taiwan University and National Taiwan University Hospital, Taipei
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
Correspondence: Professor Andrew T. A. Cheng, Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan. Tel: +886 2 2789 9119; fax: +8862 2782 3047; e-mail: bmandrew{at}gate.sinica.edu.tw
Declaration of interest None. Funding detailed in Acknowledgement.
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ABSTRACT |
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Aims To examine the patterns of psychiatric morbidities contributing to accidental death in three ethnic groups (Han, Ami and Atayal) in Taiwan.
Method A casecontrol psychological autopsy was conducted among 90 accidental deaths (randomly selected from a total of 413) and 180 living controls matched for age, gender, ethnicity and area of residence in Taiwan.
Results The risk of accidental death was significantly associated with alcohol use disorder and with other common mental disorders. When jointly considered, it was greatest when these two types of disorders co-existed, followed by common mental disorders alone. The risk of accidental death increased with the number of comorbid conditions.
Conclusions The prevention of accidental death should be incorporated into preventive psychiatry, not just for alcohol use disorder, but also for all other common mental disorders.
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INTRODUCTION |
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METHOD |
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Based on the number of accidental deaths occurring in each country in the year before the study, 30 cases were randomly selected with probability proportional to size for each type of accidental death in people aged 15 years or over in each of the three ethnic groups. The total numbers of accidental deaths were 59, 80 and 274 among the Atayal, Ami and Han, respectively, during the study period. Overall, 81% of the deaths were men, and 66% were the result of road traffic accidents. The distributions of age, gender and accident type were similar in the study sample and in the total group of accidental deaths, with no statistically significant difference. Every case was matched with two living controls for age (plus or minus 5 years), gender, ethnicity and area of residence (same village or district) during the year before the death, randomly selected from the census record for the relevant area of residence.
Ascertainment of accidental death
In Taiwan, a death verdict of unnatural cause is jointly assigned by a
prosecutor and a coroner, whose main concern is the possibility of homicide.
They usually carefully inquire for any evidence of suicide and accident,
because such a verdict helps to exclude the possibility of homicide. As
previously reported (Cheng,
1995), accident is often recorded as the cause of unnatural deaths
that were actually suicide (e.g. by drowning, poisoning or falling) on the
official death certificates to avoid any argument with insurance agencies and
the dead persons relatives. However, the officials do quite accurately
differentiate between suicide, accident and homicide, and record the actual
cause of death in their confidential inquest notes.
In view of this, in the first stage of ascertainment of accidental death the research team jointly examined the inquest notes of consecutive unnatural deaths (including post-mortem reports) and interviewed prosecutors and coroners within a few days after the death to collect relevant information, including any suicidal behaviour (threats, warnings and notes), mental illness, serious life events and the circumstances in which the incident occurred. The team then reclassified all unnatural, non-homicidal deaths during the research period as suicide (n=47), accident (n=413) or undetermined (n=2), by joint discussion on a weekly basis. The second stage of case identification was the random selection of cases from the accident group.
Fieldwork
The review board of the National Science Council, Taiwan, approved this
study. Key informants in the sample cases, including close relatives of the
dead person and significant others, were contacted approximately 1 month after
the death occurred. A direct home visit, introduced by a public health nurse
or local civil servant, was arranged in order to conduct a psychological
autopsy interview. Informed consent was obtained from the key informants after
detailed explanation of the purpose and interview procedures of this study,
and confidentiality about interview records was assured. After the completion
of the interview for each accidental death, two controls were selected from
the local census record, and their key informants were briefly interviewed,
with informed consent. A research psychiatrist (A.T.A.C.) and two clinical
psychologists (one of them from an aboriginal ethnic group) conducted the
interview separately. All interviewers had years of experience in field
interviews related to mental illness and had participated in the previous
psychological autopsy study of suicide among the same groups
(Cheng, 1995;
Cheng et al,
2000).
Two deaths in the sample (both of men: one drowned) were judged to be suicide from our psychological autopsy interview. Both men were found to have had major depression with clear suicidal ideation and communication before death. These cases were replaced by two subsequent cases of accidental death, randomly drawn from the same ethnic group.
Several key informants were identified for most cases and controls. The mean number interviewed was 13 for cases (s.d.=2.2) and 12 for controls (s.d.=2.1). In 97.8% of both accidental deaths and controls, we interviewed family members who had lived with the individual before death. We were able to interview at least two key informants for each of the cases and the controls.
Psychological autopsy interview
The psychological autopsy interview was modified from a version used in our
earlier suicide study among the same ethnic groups in East Taiwan
(Cheng, 1995). In this
modification, we retained several parts of the original interview, including
questions on medical and psychiatric history and clinical conditions
(including the use of alcohol and drugs) at the time of death (122 items), and
associated demographic and psychosocial factors (146 items). Additional
sections were designed to obtain information about personal and environmental
conditions for various types of accidents in cases (43 items), as well as the
previous history of accidents in both cases and controls (4 items), making a
total of 315 items. A space was provided for descriptive information about the
scene of the accident. Audiotape recordings of several interviews were made,
with the interviewees informed consent.
The interview records of cases and controls were jointly reviewed by the interviewers to reach a consensus. Any residual disagreement was then clarified by reference to the tape-recordings and/or further visits to the interviewees.
Reliability of psychiatric assessment
The interrater reliability of the psychological autopsy interview was
investigated in the earlier suicide study
(Cheng, 1995). Using the
results of a pre-test among 10 suicides from all three groups, the kappa
coefficients between the three raters at item level were found to range from
0.78 to 1.00. Psychiatric diagnoses of cases and controls were made according
to DSMIIIR (American
Psychiatric Association, 1987) by A.T.A.C., who was not masked to
case-control status. However, the clinical data for 15 suicides and 15
controls randomly selected from the three groups were given to another senior
psychiatrist, who was masked to their case-control status, for independent
diagnoses. Interrater reliability between the two psychiatrists was
satisfactory, with 100% agreement for major depression, substance use
disorder, adjustment disorder, schizophrenia and organic mental disorder.
Statistical analysis
First, descriptive statistics were used to present incidence of accidental
death, the distribution of demographic characteristics and types of accident,
and frequencies of psychiatric diagnoses in cases and controls. Since our
cases and controls were individually matched, conditional logistic regression
was next applied to assess the risk of accidental death. Univariate regression
analysis was then performed to calculate the odds ratios and 95% confidence
intervals of accidental death for individual diagnostic categories. Finally,
multivariate regression analysis was used to examine the interactive effects
of all the significant mental disorders and to test whether the effect of
mental disorders varied across the three ethnic groups. Statistical analyses
were performed using SAS version 8.2 (SAS Institute Inc., Cary, NC, USA). The
pre-selected alpha level was defined as P<0.05.
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RESULTS |
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Characteristics of the study sample
Among the case group, there were more men than women in all three ethnic
groups, ranging from 70% in the Han group to 83% in the Atayal group
(Table 1). There was a tendency
for those in the Atayal group to be younger than in the Ami and Han groups,
whereas there were more older people in the Han group. The difference was,
however, only marginally significant (2=8.91, d.f.=4,
P=0.063). No statistically significant difference was observed among
the three groups in terms of gender distribution (
2=1.67,
d.f.=2, P=0.434) and accident type (
2=0.38, d.f.=2,
P=0.828). In nearly two-thirds of the cases death was due to a
traffic accident, across all three groups. Falling was the second most common
cause in all three groups, and its incidence was highest in the Atayal, who
live in mountainous areas.
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Distribution of mental illness
Table 2 presents the
percentages of individual DSMIIIR Axis I diagnoses among cases
and controls. In all three ethnic groups, the most prevalent diagnoses were
substance use disorders (largely alcohol), followed by depressive disorders
(mainly major depression) in both cases and controls. The main difference
between cases and controls was the generally higher rates of morbidity in all
diagnostic categories in the former, especially substance use disorders.
Comorbid conditions were more prevalent than single illnesses among cases,
whereas single illness was more prevalent than comorbidity among controls in
all groups.
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In both cases and controls, rates of total psychiatric morbidity were significantly higher in the two aboriginal groups than in the Han group; this difference was evident mainly for depressive disorders and substance use disorders, and was not seen in anxiety and adjustment disorders. The two aboriginal groups also had significantly higher rates of comorbid conditions than the Han group.
Mental illness and the risk of accidental death
Table 3 lists the odds
ratios of accidental death for the major DSMIIIR diagnostic
categories. For the whole group, the risk of accidental death was
significantly higher for all diagnostic categories (depressive, anxiety,
adjustment and substance use disorders). Substance use disorders (largely
alcohol) were significantly associated with the risk of accidental death in
all three ethnic groups, whereas the effect of depressive disorders was
significant only in the Atayal group; the odds ratios for anxiety and
adjustment disorders were not significant in all three groups. The odds ratios
for any mental disorder other than substance use disorders were mainly
significant in the two aboriginal groups. However, the presence of any mental
disorder significantly increased the odds ratios of accidental death in all
three groups. The effects of individual diagnostic categories on the risk of
accidental death did not differ significantly across the three groups.
However, the magnitude of association between accidental death and any mental
disorder other than substance use disorder was significantly greater in the
Atayal than in the Ami and Han groups. There was no significant interaction
between either the number of informants or the type of accident (traffic
v. non-traffic) and each of the diagnostic groups, including
alcoholism, with regard to the risk of accidental death.
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The risk of accidental death was examined for various combinations of
substance use disorders and other mental disorders. The magnitude of
association was greatest if both types of disorder coexisted, and was also
significant for other mental disorders alone, but was not significant for
substance use disorders alone (Table
3). The rate if substance use and other disorders coexisted was
highest among the Atayal (66.7%), followed by the Ami (53.3%) and Han (13.3%)
groups (2=18.72, d.f.=2, P<0.001). In multivariate
analysis, there was no significant interaction between substance use disorders
and other mental disorders, or between the former and any of the other three
diagnostic categories, with regard to the risk of accidental death.
When the risk of accidental death was examined for single and comorbid psychiatric conditions, the odds ratios were found to be significant for both in the total group. The risk of accidental death when comorbidity was present was nearly four times that for single morbidity, and nine times that for no morbidity. The risk of accidental death if comorbidity was present was significant in all three groups. When the effect from the comorbidity status was treated as a linear variable in the order no morbidity, single morbidity and comorbidity, the result showed no departure from linear trend (goodness-of-fit test statistics=0.48, d.f.=1, P=0.488). Therefore, the presence of one more disorder was associated with a three times higher likelihood of accidental death. This apparent linear trend effect from the number of comorbid psychiatric disorders was noted in all three ethnic groups (Table 3).
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DISCUSSION |
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Previous research on accidents and accidental death has investigated general population birth cohorts (Neeleman et al, 1998), psychiatric patients (Black et al, 1985; Martin et al, 1985; Hiroeh et al, 2001) and individuals with a history of accidents or a verdict of accidental death (e.g. Holding & Barraclough, 1977; Ruschena et al, 1998) by retrospective review of coroners inquest notes and/or medical records. To our knowledge, this is the first case-control psychological autopsy study that has systematically investigated the individual and combined effects of psychiatric morbidity on the risk of accidental death using the current diagnostic system.
Magnitude of psychiatric morbidity in accidental deaths
The high frequency of total psychiatric morbidity among accidental deaths
in this study (50.086.7% in the three ethnic groups) is comparable with
the figure from an earlier study in London
(Holding & Barraclough,
1977). The latter assigned psychiatric diagnoses in a total of 110
cases of accidental death based on coroners inquest notes; medical
(psychiatric) records were available for 50% of the cases. The percentages of
those who were mentally ill, mentally fit and undiagnosable were 60%, 18% and
22%, respectively. It is speculated that the rate of mental illness in that
study might have been higher if a psychological autopsy had been carried out.
Although the rates of depressive illness are similar in the two studies, we
found a much higher rate of alcohol use disorder; this is possibly due to the
fact that the earlier study only made a primary diagnosis with no report on
comorbidity. In fact, high blood alcohol levels were found post-mortem in 55%
of their cases.
Alcoholism and other mental disorders
Our finding that alcohol use disorder was the most significant mental
disorder related to accidental death was consistent with previous studies
(e.g. Brewer et al,
1994; Smith et al,
2001). Accident victims with alcoholism might not have been drunk
at the time of the accident, but the impairment of attention and driving
performance due to recent or long-term use of alcohol could have put them in
danger of traffic and non-traffic accidents
(Albery et al, 2000;
Cremona, 1986).
The effect of other common mental disorders on the risk of accidents has been relatively underestimated (Ruschena et al, 1998; Hiroeh et al, 2001). Our finding of a higher incidence of accidental death and a greater effect of other common mental disorders on the risk of accidental death in the Atayal sample may suggest that the prevention of mental disorder should be the target of prevention of accidental death in this population. It is likely that common mental disorders may exert a significant risk for accident either by themselves, or act as a risk factor for and coexist with substance use disorders.
Suicide v. accidental death
This study and the previous suicide study
(Cheng, 1995) were conducted in
the same Taiwanese population using the same methods and the same research
team. Both studies showed high rates of mental disorders in those who died as
a result of suicide or accident, the two types of unnatural non-homicidal
deaths (Rorsman et al,
1982; Cheng, 1995;
Harris & Barraclough,
1997; Ruschena et al,
1998; Hiroeh et al,
2001). Although rates of alcoholism were similar in cases of
suicide (44%) and accidental death (54%), the corresponding figures for major
depression were apparently higher in suicide (87%) than in accidental death
(30%). Moreover, both adjustment disorders (18%) and anxiety disorders (12%)
were more prevalent in cases of accidental death than in suicide. In
case-control analysis, only major depression and alcoholism were significant
antecedents for suicide, whereas alcoholism and all types of common mental
disorders were predictive of accidental death. It is likely that certain core
symptoms of common mental disorders, including poor sleep, fatigue and poor
concentration, are the key psychopathological features precipitating
accidents.
Ethnic differences
Among the three ethnic groups, the odds ratios for substance use disorders
and other mental disorders on the risk of accidental death were greater in the
Atayal than in the Ami and Han samples. Among the three groups, rates of
comorbidity were also highest in the Atayal
(Table 3). Conversely, the Han
sample had the lowest morbidity rates of nearly all kinds of psychiatric
disorders among both accidental death and control groups. The excess of
alcohol use disorder in the Atayal was also found in the earlier study of
suicide among the same groups (Cheng,
1995). The evidence has suggested that poor mental health in the
Atayal may have substantially contributed to their having the highest risk for
both accidental death and suicide.
Strengths and limitations of the study
The major strengths of this study include its matched case-control design,
with a representative sample randomly selected from the original population of
accident victims in the three ethnic groups; the use of the same design and
assessments for cross-ethnic comparisons; the careful ascertainment of the
causes of death by examining the confidential inquest notes and the immediate
interview with the coroner; and the optimal strategy for psychiatric diagnosis
made by research psychiatrists with extensive experience and good reliability
in studies of suicide and alcoholism
(Cheng, 1995; Cheng & Chen, 1995), based
on information gathered by interviewing key informants, who nearly all had
lived with the accident victims before the incident occurred. These strengths
are believed to have given this study good internal validity.
Findings in this study must be interpreted in the light of the methodological limitations of psychological autopsy. These include the accuracy of coroners reports, the possibility of the underreporting of psychiatric symptoms and illness by informants, and any systematic bias from the interviewers. The main problem regarding the use of coroners verdicts on unnatural death is that a proportion of deaths by suicide have often been misclassified as accidental death, for a number of reasons (Neeleman & Wessely, 1997). The strategy for the ascertainment of the causes of death employed in this study is believed to have satisfactorily overcome this problem. Our in-depth psychological autopsy interview further identified two deaths as suicide among the case group. Previous studies have proved that information from proxy respondents is a valid source of data in determining psychiatric diagnosis (Kelly & Mann, 1996; Conner et al, 2001a) and other correlates (Nelson et al, 1990; Conner et al, 2001b). In a case-control study, the optimal strategy to minimise any systematic bias is to interview all informants using the same assessments. Only a few studies (Cheng, 1995; Gould et al, 1996) apart from ours have done so. The satisfactory ad hoc and post hoc interrater reliability studies are believed to have substantially reduced the possibility of systematic bias from the interviewers (Cheng, 1995). However, in view of the purposeful sampling of accidental deaths in three ethnic groups in East Taiwan, the external validity of this study for the entire Taiwanese population needs to be examined.
Implications of findings
Findings in this study imply that the prevention of accident or accidental
death is likely to be closely related to the prevention of mental illness.
Apart from the well-established policy of placing restrictions on alcohol
drinking while driving or performing other activities that carry a high risk
of physical harm, we should also emphasise the importance of early
recognition, accurate diagnosis and effective treatment of substance use
disorders (especially alcoholism) and all common mental disorders. In addition
to potential environmental risk factors, the possible effect of common mental
illnesses should be examined for any society or ethnic group with a high
incidence of accidental deaths, so that preventive measures can be
considered.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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REFERENCES |
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Received for publication January 5, 2004. Revision received August 6, 2004. Accepted for publication August 6, 2004.
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