Centre for Child and Adolescent Psychiatry, PO Box 26, Vinderen, N-0319 Oslo, Norway
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ABSTRACT |
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Aims To investigate this excess mortality by calculating standardised mortality ratios (SMRs) relative to cause of death, diagnosis, cohort and age.
Method A nationwide Norwegian sample of 1095 former adolescent psychiatric in-patients were followed up 15-33 years after first hospitalisation by record linkage to the National Death Cause Registry.
Results The SMR was significantly increased for almost all causes of death investigated. In males, all psychiatric diagnoses had significantly increased SMRs, whereas in females, organic mental disorder, anxiety disorder and affective disorder had non-significantly increased SMRs. The SMR was significantly elevated for all age-spans and cohorts investigated.
Conclusions A broad prevention strategy is needed to combat the increased mortality rates found in adolescent psychiatric in-patients.
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INTRODUCTION |
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METHOD |
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For these 588 males and 507 females, mean age was 15.0 years at admission (s.d.=1.6, range=11-22) and 39.5 years at follow-up (s.d.=5.5, range=28-51). The mean follow-up period from first admission was 24.5 years (s.d.=5.5, range=15-33). The population was followed for a total of 25 268 person-years.
Based on the hospital records, all patients were rediagnosed according to the diagnostic criteria in DSM-IV (American Psychiatric Association, 1994). An interrater reliability study yielded satisfactory results, with kappa=0.79. The largest diagnostic group was disruptive behaviour disorder (DBD), which comprised 55.3% of the patients. A total of 13.9% had a personality disorder, and a psychotic disorder was found in 8.9% of the patients. The rest of the population consisted of about equal groups with mood disorder, anxiety disorder, psychoactive substance use disorder (PSUD) and organic mental disorder, with the remainder suffering other mental disorders. Comorbidity was frequently encountered, with 51% of the patients having more than one disorder. The disorder dominating the clinical picture was considered to be the main diagnosis. Psychoactive substance use disorder was the comorbid disorder most often reported, with 36.5% of those with DBD having a concurrent PSUD. Patients with DBD were dichotomised according to concurrent PSUD or not.
Statistical methods
The observed number of deaths in the study population and the causes of
these deaths were determined by linkage of the patient list to the National
Death Cause Registry. The register is based on personal identification numbers
and includes all death certificates for the Norwegian population. The cause of
death had been established in all cases and was recorded according to the
ICD-9 classification (World Health
Organization, 1977).
For each patient, the gender, birth year and first admission year were recorded, together with diagnosis at hospitalisation and, when applicable, year and cause of death. Hospital admissions and deaths were averaged to have occurred in the middle of the calendar year. Thus, the admission year and the death year counted as half a year, and each interposed year counted as one year. For people who did not die, full person-years were registered up to and including 1995, the last year of the observation. Person-years in the study were arranged according to birth year in cohorts.
To calculate the expected mortality in the corresponding cohorts in the general Norwegian population, mortality data pertaining to the total Norwegian population were employed for all cohorts of interest, with calculations performed for each gender separately. The mortality tables arrived at in this manner could then be used to calculate the expected numbers of deaths by cause of death, mental disorder, cohort and age for each gender.
The SMR is the observed number of deaths divided by the expected number of deaths, multiplied by 100. To test the statistical significance of the SMR we assumed that the observed number of deaths followed a Poisson distribution. Confidence intervals for SMR were computed using the CIA computer program (Gardner & Altman, 1989a). A 95% confidence interval (95% CI) was chosen. The SMR is significantly elevated if the lower confidence interval is >100 and significantly reduced when the upper confidence interval is <100.
We wanted to compare the SMRs found for different cohorts in a meaningful way. To do this we chose the method developed by Ederer & Mantel (1974) and recommended by Gardner & Altman (1989b). The method gives the confidence interval for the ratio between two standardised ratios. A 95% CI was chosen for this procedure also.
The SMRs investigated
First, the gender-specific all-causes SMRs were calculated. Next, the
gender-specific SMRs for natural (malignant neoplasms, circulatory disorders
and other somatic disorders) and unnatural (suicide, homicide, drug overdose
death, accident and other violent) causes of death were investigated. The
gender-specific all-causes SMRs were calculated for the main categories of
DSM-IV mental disorders at index hospitalisation. The total patient sample was
then dichotomised into two cohorts on the basis of year of birth. A total of
532 patients were born during 1945-1955, whereas the rest (563 patients) were
born during 1956-1968. Gender-specific all-causes SMRs were investigated for
these two cohorts. Next, the observation period for each patient was divided
into three age-spans: from first hospitalisation up to the age of 25 years;
between the ages of 25 and 34 years; and 35 years and above. Gender-specific
all-cause SMRs were then calculated for these ages.
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RESULTS |
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Looking at the relative contribution of unnatural and natural causes of death to the overall mortality, we found that unnatural causes accounted for 75.2% of all deaths in males and for 76.2% of all deaths in females. Taking into account the expected mortality rates, we found that unnatural deaths accounted for 77.6% of all excess deaths in males and 83.2% of all excess deaths in females.
Mental disorder-specific SMRs
In males, all-causes SMRs were significantly raised in all psychiatric
disorders, ranging from 2750 in PSUD to 390 in psychotic disorders. In
females, SMRs were significantly raised in all disorders except organic
disorders, affective disorders and anxiety disorders. In females, the
mortality risk was highest in PSUD (28 times that expected), followed by a
mortality risk of 11 times that expected in psychotic disorders. The SMRs,
including the 95% CIs, for all the mental disorders investigated are given in
Table 2.
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Cohort-specific SMRs
The cohort-specific SMRs were significantly elevated for both genders in
both cohorts investigated. In males, the mortality risk for the older cohort
was five times that expected but in the younger cohort it was 10 times that
expected. In females, the mortality risk was six times that expected in the
older cohort and nine times that expected in the younger cohort. The
gender-specific SMRs found for the two cohorts, including the 95% CIs, are
given in Table 3.
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Investigating the ratio between these SMRs (Ederer & Mantel, 1974), we found that in males the SMR>1956 : SMR<1956 ratio was 2.04 (95% CI=1.37-3.15), indicating that the increase was significant. In females, the corresponding ratio was 1.47 (95% CI=0.29-1.64), indicating that the increase was non-significant.
Age-specific SMRs
The SMR was significantly raised in both genders for all three age-spans
investigated. The mortality risk was highest in the 2534-year age-span in
both genders, with a mortality risk nine times that expected in males and 10.5
times that expected in females. Gender-specific SMRs, including the 95% CIs,
for the three age-spans investigated are given in
Table 4.
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DISCUSSION |
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Most other studies rely on the old diagnoses given at discharge from hospital (Goldacre & Hawton, 1985; Kuperman et al, 1988; Rydelius, 1988; de Chateau, 1990; Larsen et al, 1990; Östman, 1991). This study has rediagnosed all patients using DSM-IV, a criterion-based diagnostic system currently in widespread international use. An interrater study with satisfactory results was conducted to ensure the quality of the diagnostic procedure.
The population investigated does evidently consist of the most severe cases in the country over the admission period, thus representing a population of worst cases adolescent psychiatric in-patients. One important question is the degree to which the results can be generalised to adolescent psychiatric in-patients of today. This is a problem inherent to all long-term follow-up studies. Although the overall composition of adolescent psychiatric in-patients most likely has changed considerably over these years, it might be that a sample of the most disturbed patients has not changed to the same extent. The most disturbed adolescent psychiatric patients of today have a high frequency of comorbidity (Lewinsohn et al, 1995), and the picture is often complicated by drug misuse (Bukstein et al, 1989). These characteristics also apply to our study population.
Cause-specific SMRs
In their meta-analysis, Harris & Barraclough
(1998) found an all-causes SMR
of 448 in male and 367 in female child and adolescent psychiatric patients.
The higher rates in our sample might be due partly to the high proportion of
PSUD and other comorbidity. It might also be that a population of mixed child
and adolescent psychiatric patients carries a lower mortality risk than a pure
adolescent psychiatric population. Our study population consisted of
in-patients only who may have a higher mortality risk than a mixture of in-
and out-patients. In the meta-analysis, adult psychiatric in-patients had
generally lower SMRs than ours. Our results were more similar to the SMR of
599 found in a probationary school clientele
(Rydelius, 1988).
Our finding of unnatural causes accounting for 75.2% of all deaths in males and for 76.2% of all deaths in females is in accordance with Harris & Barraclough's meta-analysis (1998), which found that child and adolescent psychiatric patients had a high percentage of unnatural deaths (>70%). Also, regarding excess mortality, our results are in line with the meta-analysis, which demonstrated an excess from unnatural causes of about 80%. The findings are similar to those of de Chateau (1990), who found that 82% of the deaths occurring in his sample from a child guidance clinic were caused by suicide, homicide, accidents or PSUD.
The suicide risk in males was close to seven times the suicide risk in the general population, and it was even more markedly raised (19 times) in females. These suicide rates are far above the suicide risk found in child and adolescent psychiatric patients in the meta-analysis of Harris & Barraclough (1998) and are comparable only to the SMRs of 960 in male and 1244 in female adult psychiatric in-patients in the same review article. Our finding of a higher suicide SMR in females than in males is concordant with studies of adult patients with various mental disorders (Harris & Barraclough, 1998).
The increased risk of natural deaths is comparable to that found in most categories of psychiatric patients investigated (Harris & Barraclough, 1998), and might be due to poor social circumstances, a high frequency of heavy smokers and somatic complications due to alcohol and drug misuse, that is, cirrhosis of the liver and AIDS. It has been suggested also that the increase might be partly because patients with serious, often undetected, physical disorders are selectively referred to psychiatric clinics (Martin et al, 1985).
Mental disorder-specific SMRs
As there has not, to our knowledge, been any large study of mortality in
adolescent psychiatric in-patients relative to specific mental disorders, we
found a comparison of our results with those of Harris & Barraclough's
(1998) comprehensive
meta-analysis of mortality in various mental disorders in general to be most
meaningful, although they pertain to adult patients. In the vast majority of
disorders investigated by us, the mortality risk was higher in our adolescent
population than in the adult populations in the meta-analysis.
We have reported elsewhere (Kjelsberg & Dahl, 1999) that 72% of our patients with DBD, most of them males, had a criminal record at follow-up. We therefore compared our results regarding this particular patient group with those of Reiter (1974), who investigated a group of mentally ill males in a forensic psychiatric unit in Sweden. He found an SMR of 340, which is still well below the SMRs of 1160 and 578 found in our DBD males, relative to concurrent PSUD or not.
The mortality risk in our patients with psychotic disorders was markedly higher than in any of the psychotic subgroups of Harris & Barraclough's (1998) meta-analysis. This might imply that the mortality risk in psychotic disorders is highest in patients with adolescent debut. We found a markedly higher mortality risk in females than in males with psychotic disorder, a gender difference not found in adults in the meta-analysis. Females with an adolescent debut of psychosis might be a high-risk group for premature death.
Comparing our results in the PSUD group with those of adult mixed-drug abusers in the meta-analysis, our all-causes SMRs of 2750 in males and 2810 in females were high compared with their corresponding ratios of 495 and 444. This marked difference is most likely due to our selected material of severely disordered and often comorbid in-patient drug addicts.
Cohort-specific SMRs
The increase in SMR from the 1945-1955 cohort to the 1956-1968 cohort can
be explained by a marked increase in overdose deaths and suicides from the
older to the younger cohort, an increase that is paralleled in the general
population of Norway. Only the increase in the male population was
significant, though. It is important to investigate further whether this
cohort effect of increased mortality in adolescent psychiatric in-patients
continues in the future.
Age-specific SMRs
The pattern of an initial increase in SMR in adolescents throughout their
mid-20s and then a subsequent decrease in SMR has been found in other
populations too. Zilber (Zilber et
al, 1989) found that the SMR increased from 417 in
10-19-year-olds to 798 in 20-39-year-olds, after which the SMR steadily
decreased down to 163 in those 70 years or older. Other studies have found
similar trends, although less marked (Black
et al, 1985; Martin
et al, 1985; Casadebaig & Quemada, 1989;
Amaddeo et al, 1995;
Hansen et al, 1997).
It is important to realise, however, that all these results pertain to
psychiatric patients in general, and not to adolescent psychiatric in-patients
growing older, as in our sample.
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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 May 24, 1999. Revision received September 8, 1999. Accepted for publication September 10, 1999.
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