Risk factors of suicide among . schizophrenics 4
.
Cheng KK, Leung CM, Lo WH, Lam TH. Risk factors of suicide among schizophrenics. Acta Psychiatr Scand 1990: 81: 220-224.
I
This case control study included 74 Chinese schizophrenics (DSM-I11 criteria) who died of suicide and 74 age- and sex-matched nonsuicide schizophrenics. Sociodemographic variables were unrelated with suicide. Associations were found between suicide and severity of illness (more frequent admissions, higher dose of medication and earlier appointments), history of major depressive episodes and suicidal attempts, last admission for reasons other than schizophrenic symptoms alone, and suicidal ideas on mental state examination. The last 2 factors, together with the maintenance dose of medication, were identified as the most important risk factors by logistic regression analysis.
The risk of suicide among schizophrenic patients is well known. It has been estimated that 10% of all schizophrenics die of suicide (1). Drake et al. (2) reviewed the numerous studies in the literature on suicide among schizophrenics and pointed out that many of them were either descriptive only or were poorly controlled because of diagnostic heterogeneity. Moreover, in the group of reports they designated as well controlled, the numbers of suicides were all relatively small, ranging from 3 to 40. The small sample sizes inevitably limit the statistical power when multiple factors are considered in the analysis. In the Chinese population, not much is known about suicidal behavior among schizophrenics. Law (3) compared 23 Chinese schizophrenics who committed suicide and 23 nonsuicide schizophrenics in Hong Kong but found no significant differences between the 2 groups, except that mental relapse within the last 3 months was more common in the male suicides than in their controls. A descriptive study on a large series of schizophrenic suicides was reported recently (4). Interesting features were found among the patients who killed themselves. However, there was no control group for comparison, so risk factors could not be determined. This study was therefore undertaken to compare a large group of Chinese schizophrenics who committed suicide with a group of nonsuicide schizophrenics. Material and methods
This study was carried out in the 2 outpatient clinics of the Government Mental Health Service on the 220
K. K. Cheng’,
C. M. Leung2, W. H. Lo2,
T. H. Lam’
’
Department of Community Medicine, University of Hong Kong, Mental Health Service, Medical and Health Department, Hong Kong
Key words: suicide; schizophrenia
Dr. K.K. Cheng, Department of Community Medicine, University of Hong Kong, Li Shu Fan Building, Sassoon Road, Hong Kong Accepted for publication September 16, 1989
island of Hong Kong. All patients who were registered in the 2 clinics and died by suicide between 1981 and 1985 were included. All available inpatient and outpatient records, charts and discharge summaries of these patients were examined and data extracted. DSM-I11 ( 5 ) criteria were applied retrospectively by one of us (C.M.L.); 74 patients with chronic or subchronic schizophrenia were identified as cases. Each case was then matched for sex and age (within 5 years) with another schizophrenic patient (also based on DSM-I11 criteria) of the same clinic who had a hospital number closest to that of the case. The cases and controls were compared for a number of sociodemographic and psychiatric variables. Univariate analyses with t-tests, chisquare and Fisher’s exact tests were used. Further analysis was done using logistic regression to study the relationship between the dependent variable (suicide or nonsuicide) and a number of independent variables that were found to be significantly associated with suicide in univariate analysis. By this method, the risks associated with the variables were estimated after adjusting for each other. As the cases and controls were only matched for sex and age, the analysis can be performed as if there were no matching (6). The LOGRESS program (7) was used for this purpose. Results
The characteristics of the 74 suicide cases were described in an earlier report (4). All the 74 suicide cases and 74 controls were of Chinese origin and were outpatients at the 2 clinics. Forty-three suicides were male and 3 1 were female.
Suicide among schizophrenics The mean ( & SD) age at death of the cases was 31.3 5 9.1 years, and for the controls, 30.9 5 9.3 years (NS). Sociodemographic variables
Twenty-seven of the 74 cases were not born in Hong Kong. Thirty-five suicides had received education up to secondary level or above and an equal number of them were employed. Twenty of them were married at the time of death. Only 5 cases lived alone. No significant difference was found between the cases and the controls in any of these variables. Psychiatric variables
Onset and duration of illness. There was no significant difference in the mean ages at onset of illness between the cases (22.4 years) and the controls (22.7 years). Similarly, the mean duration of illness of the cases of 8.3 years was very close to the mean of 8.4 years in the controls. Admission history. Fifty-five cases had been admitted at least once to psychiatric wards, compared with 52 controls. The 55 cases had a mean admission frequency of 2.7 times, while that of the 52 controls was only 2.0 times ( t = 2.09, df = 105, P < 0.05). The reasons for the last admission are shown in Table 1. Both depression and suicidal ideas or suicide attempt occurred more frequently during the last admission among the cases than the controls. When the 2 sexes are separately considered, the difference was significant in females only for depression and males only for suicide attempt. More cases than controls exhibited violent acts towards other people or objects immediately before the last admission. Differences were also noted between the cases and the controls in each sex (NS). No significant difference was found between the cases and the controls in the frequency of being Table 1. Reasons for the last admission - cases vs controls Males
Schizophrenic symptoms Depression Suicidal ideas or suicide attempts Violent acts Hospital order
Females
Case n=34
Control n=32
P
Case n=21
29 3
30 2
NS NS
18 1
19 0
0.01
9 1 4
1 1
0.01 0.06 0.06
6 2 1
3 0
NS NS
1
NS
0
Control n=20
P
NS
* By chi-square test with continuity correction (df = 1) or Fisher’s exact test; N.B. There was more than one reason for some admissions.
involuntarily admitted to hospital after committing criminal acts. Only 30/55 of the cases compared with 8/52 of the controls were last admitted for reasons other than schizophrenic symptoms alone (x’ = 16.2, df = 1, P < 0.0001). Drug treatment. Twenty-seven cases and 17 controls were receiving depot intramuscular injection of antipsychotic medication (NS). The antipsychotic medication of each subject was converted to equivalent daily dose of chlorpromazine for comparison. The cases were receiving a mean equivalent daily dose of 484 mg compared with 263 mg among the controls ( t = 3.30, df = 135, P < 0.0 1). The differences between the cases and the controls were also significant when the 2 sexes were considered separately. Nine cases were on antidepressants compared with 7 controls (NS). Lust psychiatric contact. Four cases and 7 controls had stopped attending follow-up for 6 months or more by the time of death of the cases (NS). Among the rest for whom information on the last psychiatric contact was studied, 15/70 of the cases and 10/67 of the controls exhibited active symptoms when last seen by their psychiatrists (NS). When individual symptoms were looked at, depression was more frequently seen in the male cases (5/40) than their controls (0/42) (Fisher’s exact test, P < 0.05). This difference was, however, not significant in females (1/30 compared with 1/25). Suicidal ideation was elicited during the last 2 consultations in 8/70 of the cases compared with only 1/67 of the controls (Fisher’s exact test, P < 0.05). There were no significant differences in each sex. No significant difference was detected in the frequencies of delusions or hallucinations between the cases and the controls. At the last contact, the cases were given an earlier appointment date on average than the controls: 4.3 weeks compared with 5.7 weeks ( t = 2.60, df = 136, P < 0.05). Thirty-four of the 71 cases had been seen by a psychiatrists in the week preceding their deaths. Past suicide attempts. More cases (27/74) than controls (1 1/74) had history of one or more suicidal attempts (x’ = 7.97, df = 1, P < 0.01). The difference was significant between the female cases and controls (x’ = 6.70, df = 1, P < 0.05) but not in the males. Among the 27 cases and 11 controls who had history of previous suicide attempts, the mean number of attempts was higher in the cases (1.7 times) than the controls (1.2 times) ( P < 0.05). Depressive episode. Twenty cases compared with 9 controls had at least one episode of depression that met DSM-I11 criteria for major depressive episode in the last 5 years (Fisher’s exact test, P < 0.05). The 221
Cheng et a]. Table 2. OR and 95% CI of 1 1 independent variables (each variable adjusted for age and sex) Number of previous admissions Last admission for any reasons other than schizophrenic symptoms alone depression suicidal ideas or attempts violent acts Last psychiatric consultation expressed suicidal ideas time from next appointment History of previous suicide attempts Number of previous suicide attempts Major depressive episode in last 5 years Dosage of antipsychotic medication (per 100 mg chlorpromazine or equivalent)
1.22 (1.00-1.45) 5.66 (2.37-13.49) 5.69 (1.20-27.13) 4.57 (1.43-14.55) 10.43 (1.28-84.93) 8.92 (1.09-73.17) 0.78 (0.67-0.91) 3.69 (1.59-8.54) 2.63 (1.43-4.85) 2.88 (1.18-7.011 1.22 (1.08-1.38)
difference was significant in females (Fisher’s exact test, P 0.01) but not in males. Multivariate analysis. Logistic regression was used to estimate the risks of variables that were found to be significantly associated with suicide in univariate analysis. As the controls were matched for sex and age to the cases, these 2 variables were adjusted for in the estimation of risks of all other factors. Eleven variables were found to be associated with suicide in univariate analysis: number of previous admissions; last admission for depression, suicidal ideas or attempts, violent acts or any reasons other than schizophrenic symptoms alone; expressed suicidal ideas at the last psychiatric consultation; length of time of the next appointment given from the last consultation; history and number of previous suicide attempts; history of major depressive episode in the last 5 years; dosage of antipsychotic medication the patient was on (in equivalent dosage of chlorpromazine). The odds ratios (OR) and 95% confidence intervals (CI) of these risk factors after they were adjusted for sex and age are shown in Table 2. The best logistic regression equation with the smallest number of independent variables is shown
-=
Table 3. Result of the best logistic regression equation relating suicide to various risk factors Variables
Coefficient
SE
OR
95% CI
P
1 2 3 4 5 Constant
-0.25 0.01 1.82 0.18 1.73 - 1.13
0.38 0.02 0.46 0.07 1.13 0.71
0.78 1.01 6.20 1.19 5.62
0.37-1.64 0.97-1.05 2.51-15.29 1.04-1.36 0.61-51.66
NS NS 0.01 0.01 NS
~
Likelihood ratio = 34.80, df = 5, P < 0.001. 1 = sex; 2 = age; 3 = last admission for reasons other than schizophrenic symptoms alone; 4 = dosage of antipsychotic medication (per 100 mg); 5 = expressed suicidal ideas at last consultation.
222
in Table 3. Sex and age were included in the model, as they were the matching factors. The most important risk factors were therefore last admission for reason(s) other than schizophrenic symptoms alone, dosage of antipsychotic medication and expression of suicidal ideas at the last psychiatric consultation. The last variable was of borderline statistical significance. It was included because of the high risk incurred by its presence and its clinical relevance. Addition of any other variables or interaction effects did not increase significantly the likelihood ratio. Discussion
In this study, there were 74 suicide cases and an equal number of nonsuicide schizophrenics as the comparison group. All the subjects met DSM-I11 diagnosis of chronic or subchronic schizophrenia. To the best of our knowledge, the number of subjects is larger than in any similar study previously reported. We believe that the larger sample size will considerably enhance the validity of the study as well as the power in detecting a difference in our analysis. It should be pointed out, however, that some confidence intervals of the OR were still fairly wide, because small numbers were encountered in analyzing certain variables. None of the sociodemographic variables we investigated was associated with suicide in our sample. Although it has been reported that schizophrenic patients who killed themselves tended to have more education than their controls (8), such a relationship did not exist in this study. Similar to what Roy (9) and Shaffer et al. (10) found, there was no significant difference in the proportions of suicides and controls who lived alone. Nor was marital or employment status associated with suicide, a finding similar to that of Shaffer et al. (10) but at variance with Roy (9), who found that employment (but not marital) status was associated with suicide. The suicides had a higher mean frequency of admission than the controls. This is compatible with findings elsewhere that schizophrenics who committed suicide typically experienced many relapses and hospitalizations (9, 11, 12). Whether chronicity is associated with suicide cannot be answered by the present study. We found that both the mean age of onset and duration of illness were almost identical in the suicides and controls. However, bearing in mind that the suicides and the controls were matched for age and time of presentation (indirectly through matching of hospital number), this finding should not lead to the conclusion that there is no real difference in the duration of illness of the 2 groups. The suicides were more likely than their controls to have been admitted for reasons other than schizophrenic symptoms alone during the last ad-
Suicide among schizophrenics mission, and this was one of the best predictors of suicide in multivariate analysis, with an adjusted OR of 6.20. Depression and suicidal ideas or attempts were more common among the suicides during the last hospitalization. This agrees with the finding of Roy (9) that the chronic schizophrenic patients who had been admitted because of depression or suicidal impulses were at particular risk for subsequent suicide. Differences were found in both sexes, but statistical significance was reached in females only for depression and males only for suicidal ideas or attempts. This may be explained by the small number when the sexes are considered separately. Violent acts prior to the last admission were more frequently found in the cases and this carried an almost tenfold increase in risk of suicide. This is compatible with the finding of Myers et al. (13) and is not surprising if suicide is viewed as the ultimate violent act against oneself. Whether depression is a risk factor of suicide needs to be answered by a controlled study, as it has long been recognized to be a common feature among all schizophrenics (14,15). Roy (9) reported an association between a history of major depressive episode (meeting DSM-I11 criteria) and suicide. This finding was confirmed by the present study. There were also more cases who had attempted suicide previously than controls (OR = 3.29). These 2 differences were more marked in the female when the sexes were separately analyzed, similar to what was described by Allebeck (16). The mean number of previous attempts was also higher in the suicide group. The literature is inconclusive on the role of antipsychotic medication in schizophrenic suicides (2). In this study, the mean dosage of maintenance antipsychotic drug the suicides were receiving was more than 200 mg (expressed in chlorpromazine equivalent per day) higher than the controls. Also, there were more suicides who were receiving depot injections of neuroleptic (NS). From this, one should not conclude automatically that antipsychotic drugs may cause schizophrenic suicide, although biological plausibility is provided by the claim that these drugs may remove psychotic symptoms prematurely and increase depression (17). Alternatively, we propose that both suicide and higher dosage of medication reflect the severity of the schizophrenic illness, which may therefore be seen as a confounding factor. There are 2 reasons to support this hypothesis: first, patients with more severe and chronic illness often require and are prescribed a heavier maintainence dosage of medication. Second, as the appointment given to a patient can be regarded as an indicator of the psychiatrist’s assessment of the patient’s condition, the fact that the suicide cases were given on average an earlier appointment date at the last con-
tact than the controls also speaks for the severity of the former group’s illnesses. About half of the suicides in our sample were seen by their psychiatrists in the week preceding their deaths. At the last psychiatric contact, the overall proportion of subjects who exhibited active psychotic symptoms did not differ significantly in the suicide and control groups. There were also no significant differences in the proportions of subjects who were experiencing hallucination or delusion in the 2 groups. This suggested that suicide may not be linked to active psychotic activities. Accordingly, absence of such symptoms should not be a reassuring factor when psychiatrists assess the suicidal risk of their schizophrenic patients. However, 2 important differences between suicides and controls did emerge: there were more suicides than controls in whom suicidal ideation was elicited and depression was more commonly found in the male cases than their controls. In multivariate analysis, it was found that expression of suicidal ideas was one of the variables included in the best model. The point estimate of the OR was 5.62, though its C1 was very wide. There seems to be a case for the psychiatrist to try to elicit this symptom routinely when a schizophrenic patient is seen and its presence should always be viewed as a serious alarm. The idea is widely held that suicide among schizophrenics is somewhat unpredictable and recent studies (16, 18) provide some support for this belief. In the present study, however, a number of associations were found and by multivariate analysis, 3 risk factors were identified. The advantage of using these 3 variables is that they can either be identified easily and reliably from the patients’ records or be elicited-without too much difficulty by those with some training. There are, however, 2 points that must be noted in interpreting the present findings. First, the risk factors are not amenable to changes and cannot be labeled as causes of suicide as such. They should instead be treated as indicators of suicidal risk. Second, though we are aware that suicide is closely related to culture, it is not possible for us to determine whether the findings can be generalized to other cultural contexts. Despite these limitations and in view of the very limited ability to predict suicide, an assessment of suicidal risk on the basis of the 3 variables should be of potential use in preventing some hitherto elusive suicides, while the search for other unknown predictive factors is going on. On the other hand, the efficacy of prediction using these factors should be examined by further studies, preferably with a prospective design and in different cultural settings.
223
Cheng et al. Acknowledgements This work was supported by the Committee on Research and Conference Grants (337/040/0001) and Medical Faculty Research Grant Fund (362-030-3384), University of Hong Kong.
References 1. MILESCP. Conditions predisposing to suicide: a review. J Nerv Ment Dis 1977: 164: 231-246. 2. DRAKERE, GATESC, WHITAKERA et al. Suicide among schizophrenics: a review. Compr Psychiatry 1985: 26: 90-100. 3. LAW SK. Suicide - some international and Hong Kong findings. In: KHOOTP, ed. Mental health in Hong Kong, 1986. Hong Kong: Mental Health Association of Hong Kong, 1986: 266-278. 4. CHENGKK, LEUNGCM, Lo WH etal. Suicide among Chinese schizophrenics in Hong Kong. Br J Psychiatry 1989: 154: 243-246. 5. American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 3rd ed. Washington, DC: American Psychiatric Association, 1980: 181-193. 6. BRESLOWNE, DAYNE. Statistical methods in cancer research, vol. 1 - the analysis of case-control studies. Lyon: International Agency for Research on Cancer, 1980. 7. MCGEEDL. A program for logistic regression on the IBM PC. Am J Epidemiol 1986: 124: 702-705.
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8. FARBEROW N, SCHNEIDMAN E, NEURINGER C. Case history and hospitalization factors in suicides of neuropsychiatric hospital patients. J Nerv Ment Dis 1966: 142: 32-44. 9. ROY A. Suicide in chronic schizophrenia. Br J Psychiatry 1982: 141: 171-177. JH. The 10. SHAFFER JW, PERLINS, SCHIMDTCW, STEPHENS prediction of suicide in schizophrenics. J Nerv Ment Dis 1974: 159: 349-355. 11 POKORNYAD. Characteristics of forty-four patients who subsequently committed suicide. Arch Gen Psychiatry 1960: 2: 314-323. 12. YARDENP. Observations on suicide in chronic schizophrenics. Compr Psychiatry 1974: 15: 325-333. 13. MEYERSDH, NEALCD. Suicide in psychiatric patients. Br J Psychiatry 1978: 133: 38-44. 14. Hirsch SR. Depression 'revealed' in schizophrenia. Br J Psychiatry 1981: 140: 421-24. 15. The Scottish Schizophrenia Research Group: the Scottish first episode schizophrenia study. I. Patient identification and categorisation. Br J Psychiatry 1987: 150: 331-33. E et al. Risk factors 16. ALLEBECK P, VARIAA, KRISTJANSSON for suicide among patients with schizophrenia. Acta Psychiatr Scand 1987: 76: 414-419. J. A study of suicides in a mental 17. BEISSERA, BLANCHETTE hospital. Dis Nerv Syst 1961: 22: 365-369. 18. BREIERA, ASTRACHAN BM. Characterization of schizophrenic patients who commit suicide. Am J Psychiatry 1984: 141: 206-209.
.
Cheng KK, Leung CM, Lo WH, Lam TH. Risk factors of suicide among schizophrenics. Acta Psychiatr Scand 1990: 81: 220-224.
I
This case control study included 74 Chinese schizophrenics (DSM-I11 criteria) who died of suicide and 74 age- and sex-matched nonsuicide schizophrenics. Sociodemographic variables were unrelated with suicide. Associations were found between suicide and severity of illness (more frequent admissions, higher dose of medication and earlier appointments), history of major depressive episodes and suicidal attempts, last admission for reasons other than schizophrenic symptoms alone, and suicidal ideas on mental state examination. The last 2 factors, together with the maintenance dose of medication, were identified as the most important risk factors by logistic regression analysis.
The risk of suicide among schizophrenic patients is well known. It has been estimated that 10% of all schizophrenics die of suicide (1). Drake et al. (2) reviewed the numerous studies in the literature on suicide among schizophrenics and pointed out that many of them were either descriptive only or were poorly controlled because of diagnostic heterogeneity. Moreover, in the group of reports they designated as well controlled, the numbers of suicides were all relatively small, ranging from 3 to 40. The small sample sizes inevitably limit the statistical power when multiple factors are considered in the analysis. In the Chinese population, not much is known about suicidal behavior among schizophrenics. Law (3) compared 23 Chinese schizophrenics who committed suicide and 23 nonsuicide schizophrenics in Hong Kong but found no significant differences between the 2 groups, except that mental relapse within the last 3 months was more common in the male suicides than in their controls. A descriptive study on a large series of schizophrenic suicides was reported recently (4). Interesting features were found among the patients who killed themselves. However, there was no control group for comparison, so risk factors could not be determined. This study was therefore undertaken to compare a large group of Chinese schizophrenics who committed suicide with a group of nonsuicide schizophrenics. Material and methods
This study was carried out in the 2 outpatient clinics of the Government Mental Health Service on the 220
K. K. Cheng’,
C. M. Leung2, W. H. Lo2,
T. H. Lam’
’
Department of Community Medicine, University of Hong Kong, Mental Health Service, Medical and Health Department, Hong Kong
Key words: suicide; schizophrenia
Dr. K.K. Cheng, Department of Community Medicine, University of Hong Kong, Li Shu Fan Building, Sassoon Road, Hong Kong Accepted for publication September 16, 1989
island of Hong Kong. All patients who were registered in the 2 clinics and died by suicide between 1981 and 1985 were included. All available inpatient and outpatient records, charts and discharge summaries of these patients were examined and data extracted. DSM-I11 ( 5 ) criteria were applied retrospectively by one of us (C.M.L.); 74 patients with chronic or subchronic schizophrenia were identified as cases. Each case was then matched for sex and age (within 5 years) with another schizophrenic patient (also based on DSM-I11 criteria) of the same clinic who had a hospital number closest to that of the case. The cases and controls were compared for a number of sociodemographic and psychiatric variables. Univariate analyses with t-tests, chisquare and Fisher’s exact tests were used. Further analysis was done using logistic regression to study the relationship between the dependent variable (suicide or nonsuicide) and a number of independent variables that were found to be significantly associated with suicide in univariate analysis. By this method, the risks associated with the variables were estimated after adjusting for each other. As the cases and controls were only matched for sex and age, the analysis can be performed as if there were no matching (6). The LOGRESS program (7) was used for this purpose. Results
The characteristics of the 74 suicide cases were described in an earlier report (4). All the 74 suicide cases and 74 controls were of Chinese origin and were outpatients at the 2 clinics. Forty-three suicides were male and 3 1 were female.
Suicide among schizophrenics The mean ( & SD) age at death of the cases was 31.3 5 9.1 years, and for the controls, 30.9 5 9.3 years (NS). Sociodemographic variables
Twenty-seven of the 74 cases were not born in Hong Kong. Thirty-five suicides had received education up to secondary level or above and an equal number of them were employed. Twenty of them were married at the time of death. Only 5 cases lived alone. No significant difference was found between the cases and the controls in any of these variables. Psychiatric variables
Onset and duration of illness. There was no significant difference in the mean ages at onset of illness between the cases (22.4 years) and the controls (22.7 years). Similarly, the mean duration of illness of the cases of 8.3 years was very close to the mean of 8.4 years in the controls. Admission history. Fifty-five cases had been admitted at least once to psychiatric wards, compared with 52 controls. The 55 cases had a mean admission frequency of 2.7 times, while that of the 52 controls was only 2.0 times ( t = 2.09, df = 105, P < 0.05). The reasons for the last admission are shown in Table 1. Both depression and suicidal ideas or suicide attempt occurred more frequently during the last admission among the cases than the controls. When the 2 sexes are separately considered, the difference was significant in females only for depression and males only for suicide attempt. More cases than controls exhibited violent acts towards other people or objects immediately before the last admission. Differences were also noted between the cases and the controls in each sex (NS). No significant difference was found between the cases and the controls in the frequency of being Table 1. Reasons for the last admission - cases vs controls Males
Schizophrenic symptoms Depression Suicidal ideas or suicide attempts Violent acts Hospital order
Females
Case n=34
Control n=32
P
Case n=21
29 3
30 2
NS NS
18 1
19 0
0.01
9 1 4
1 1
0.01 0.06 0.06
6 2 1
3 0
NS NS
1
NS
0
Control n=20
P
NS
* By chi-square test with continuity correction (df = 1) or Fisher’s exact test; N.B. There was more than one reason for some admissions.
involuntarily admitted to hospital after committing criminal acts. Only 30/55 of the cases compared with 8/52 of the controls were last admitted for reasons other than schizophrenic symptoms alone (x’ = 16.2, df = 1, P < 0.0001). Drug treatment. Twenty-seven cases and 17 controls were receiving depot intramuscular injection of antipsychotic medication (NS). The antipsychotic medication of each subject was converted to equivalent daily dose of chlorpromazine for comparison. The cases were receiving a mean equivalent daily dose of 484 mg compared with 263 mg among the controls ( t = 3.30, df = 135, P < 0.0 1). The differences between the cases and the controls were also significant when the 2 sexes were considered separately. Nine cases were on antidepressants compared with 7 controls (NS). Lust psychiatric contact. Four cases and 7 controls had stopped attending follow-up for 6 months or more by the time of death of the cases (NS). Among the rest for whom information on the last psychiatric contact was studied, 15/70 of the cases and 10/67 of the controls exhibited active symptoms when last seen by their psychiatrists (NS). When individual symptoms were looked at, depression was more frequently seen in the male cases (5/40) than their controls (0/42) (Fisher’s exact test, P < 0.05). This difference was, however, not significant in females (1/30 compared with 1/25). Suicidal ideation was elicited during the last 2 consultations in 8/70 of the cases compared with only 1/67 of the controls (Fisher’s exact test, P < 0.05). There were no significant differences in each sex. No significant difference was detected in the frequencies of delusions or hallucinations between the cases and the controls. At the last contact, the cases were given an earlier appointment date on average than the controls: 4.3 weeks compared with 5.7 weeks ( t = 2.60, df = 136, P < 0.05). Thirty-four of the 71 cases had been seen by a psychiatrists in the week preceding their deaths. Past suicide attempts. More cases (27/74) than controls (1 1/74) had history of one or more suicidal attempts (x’ = 7.97, df = 1, P < 0.01). The difference was significant between the female cases and controls (x’ = 6.70, df = 1, P < 0.05) but not in the males. Among the 27 cases and 11 controls who had history of previous suicide attempts, the mean number of attempts was higher in the cases (1.7 times) than the controls (1.2 times) ( P < 0.05). Depressive episode. Twenty cases compared with 9 controls had at least one episode of depression that met DSM-I11 criteria for major depressive episode in the last 5 years (Fisher’s exact test, P < 0.05). The 221
Cheng et a]. Table 2. OR and 95% CI of 1 1 independent variables (each variable adjusted for age and sex) Number of previous admissions Last admission for any reasons other than schizophrenic symptoms alone depression suicidal ideas or attempts violent acts Last psychiatric consultation expressed suicidal ideas time from next appointment History of previous suicide attempts Number of previous suicide attempts Major depressive episode in last 5 years Dosage of antipsychotic medication (per 100 mg chlorpromazine or equivalent)
1.22 (1.00-1.45) 5.66 (2.37-13.49) 5.69 (1.20-27.13) 4.57 (1.43-14.55) 10.43 (1.28-84.93) 8.92 (1.09-73.17) 0.78 (0.67-0.91) 3.69 (1.59-8.54) 2.63 (1.43-4.85) 2.88 (1.18-7.011 1.22 (1.08-1.38)
difference was significant in females (Fisher’s exact test, P 0.01) but not in males. Multivariate analysis. Logistic regression was used to estimate the risks of variables that were found to be significantly associated with suicide in univariate analysis. As the controls were matched for sex and age to the cases, these 2 variables were adjusted for in the estimation of risks of all other factors. Eleven variables were found to be associated with suicide in univariate analysis: number of previous admissions; last admission for depression, suicidal ideas or attempts, violent acts or any reasons other than schizophrenic symptoms alone; expressed suicidal ideas at the last psychiatric consultation; length of time of the next appointment given from the last consultation; history and number of previous suicide attempts; history of major depressive episode in the last 5 years; dosage of antipsychotic medication the patient was on (in equivalent dosage of chlorpromazine). The odds ratios (OR) and 95% confidence intervals (CI) of these risk factors after they were adjusted for sex and age are shown in Table 2. The best logistic regression equation with the smallest number of independent variables is shown
-=
Table 3. Result of the best logistic regression equation relating suicide to various risk factors Variables
Coefficient
SE
OR
95% CI
P
1 2 3 4 5 Constant
-0.25 0.01 1.82 0.18 1.73 - 1.13
0.38 0.02 0.46 0.07 1.13 0.71
0.78 1.01 6.20 1.19 5.62
0.37-1.64 0.97-1.05 2.51-15.29 1.04-1.36 0.61-51.66
NS NS 0.01 0.01 NS
~
Likelihood ratio = 34.80, df = 5, P < 0.001. 1 = sex; 2 = age; 3 = last admission for reasons other than schizophrenic symptoms alone; 4 = dosage of antipsychotic medication (per 100 mg); 5 = expressed suicidal ideas at last consultation.
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in Table 3. Sex and age were included in the model, as they were the matching factors. The most important risk factors were therefore last admission for reason(s) other than schizophrenic symptoms alone, dosage of antipsychotic medication and expression of suicidal ideas at the last psychiatric consultation. The last variable was of borderline statistical significance. It was included because of the high risk incurred by its presence and its clinical relevance. Addition of any other variables or interaction effects did not increase significantly the likelihood ratio. Discussion
In this study, there were 74 suicide cases and an equal number of nonsuicide schizophrenics as the comparison group. All the subjects met DSM-I11 diagnosis of chronic or subchronic schizophrenia. To the best of our knowledge, the number of subjects is larger than in any similar study previously reported. We believe that the larger sample size will considerably enhance the validity of the study as well as the power in detecting a difference in our analysis. It should be pointed out, however, that some confidence intervals of the OR were still fairly wide, because small numbers were encountered in analyzing certain variables. None of the sociodemographic variables we investigated was associated with suicide in our sample. Although it has been reported that schizophrenic patients who killed themselves tended to have more education than their controls (8), such a relationship did not exist in this study. Similar to what Roy (9) and Shaffer et al. (10) found, there was no significant difference in the proportions of suicides and controls who lived alone. Nor was marital or employment status associated with suicide, a finding similar to that of Shaffer et al. (10) but at variance with Roy (9), who found that employment (but not marital) status was associated with suicide. The suicides had a higher mean frequency of admission than the controls. This is compatible with findings elsewhere that schizophrenics who committed suicide typically experienced many relapses and hospitalizations (9, 11, 12). Whether chronicity is associated with suicide cannot be answered by the present study. We found that both the mean age of onset and duration of illness were almost identical in the suicides and controls. However, bearing in mind that the suicides and the controls were matched for age and time of presentation (indirectly through matching of hospital number), this finding should not lead to the conclusion that there is no real difference in the duration of illness of the 2 groups. The suicides were more likely than their controls to have been admitted for reasons other than schizophrenic symptoms alone during the last ad-
Suicide among schizophrenics mission, and this was one of the best predictors of suicide in multivariate analysis, with an adjusted OR of 6.20. Depression and suicidal ideas or attempts were more common among the suicides during the last hospitalization. This agrees with the finding of Roy (9) that the chronic schizophrenic patients who had been admitted because of depression or suicidal impulses were at particular risk for subsequent suicide. Differences were found in both sexes, but statistical significance was reached in females only for depression and males only for suicidal ideas or attempts. This may be explained by the small number when the sexes are considered separately. Violent acts prior to the last admission were more frequently found in the cases and this carried an almost tenfold increase in risk of suicide. This is compatible with the finding of Myers et al. (13) and is not surprising if suicide is viewed as the ultimate violent act against oneself. Whether depression is a risk factor of suicide needs to be answered by a controlled study, as it has long been recognized to be a common feature among all schizophrenics (14,15). Roy (9) reported an association between a history of major depressive episode (meeting DSM-I11 criteria) and suicide. This finding was confirmed by the present study. There were also more cases who had attempted suicide previously than controls (OR = 3.29). These 2 differences were more marked in the female when the sexes were separately analyzed, similar to what was described by Allebeck (16). The mean number of previous attempts was also higher in the suicide group. The literature is inconclusive on the role of antipsychotic medication in schizophrenic suicides (2). In this study, the mean dosage of maintenance antipsychotic drug the suicides were receiving was more than 200 mg (expressed in chlorpromazine equivalent per day) higher than the controls. Also, there were more suicides who were receiving depot injections of neuroleptic (NS). From this, one should not conclude automatically that antipsychotic drugs may cause schizophrenic suicide, although biological plausibility is provided by the claim that these drugs may remove psychotic symptoms prematurely and increase depression (17). Alternatively, we propose that both suicide and higher dosage of medication reflect the severity of the schizophrenic illness, which may therefore be seen as a confounding factor. There are 2 reasons to support this hypothesis: first, patients with more severe and chronic illness often require and are prescribed a heavier maintainence dosage of medication. Second, as the appointment given to a patient can be regarded as an indicator of the psychiatrist’s assessment of the patient’s condition, the fact that the suicide cases were given on average an earlier appointment date at the last con-
tact than the controls also speaks for the severity of the former group’s illnesses. About half of the suicides in our sample were seen by their psychiatrists in the week preceding their deaths. At the last psychiatric contact, the overall proportion of subjects who exhibited active psychotic symptoms did not differ significantly in the suicide and control groups. There were also no significant differences in the proportions of subjects who were experiencing hallucination or delusion in the 2 groups. This suggested that suicide may not be linked to active psychotic activities. Accordingly, absence of such symptoms should not be a reassuring factor when psychiatrists assess the suicidal risk of their schizophrenic patients. However, 2 important differences between suicides and controls did emerge: there were more suicides than controls in whom suicidal ideation was elicited and depression was more commonly found in the male cases than their controls. In multivariate analysis, it was found that expression of suicidal ideas was one of the variables included in the best model. The point estimate of the OR was 5.62, though its C1 was very wide. There seems to be a case for the psychiatrist to try to elicit this symptom routinely when a schizophrenic patient is seen and its presence should always be viewed as a serious alarm. The idea is widely held that suicide among schizophrenics is somewhat unpredictable and recent studies (16, 18) provide some support for this belief. In the present study, however, a number of associations were found and by multivariate analysis, 3 risk factors were identified. The advantage of using these 3 variables is that they can either be identified easily and reliably from the patients’ records or be elicited-without too much difficulty by those with some training. There are, however, 2 points that must be noted in interpreting the present findings. First, the risk factors are not amenable to changes and cannot be labeled as causes of suicide as such. They should instead be treated as indicators of suicidal risk. Second, though we are aware that suicide is closely related to culture, it is not possible for us to determine whether the findings can be generalized to other cultural contexts. Despite these limitations and in view of the very limited ability to predict suicide, an assessment of suicidal risk on the basis of the 3 variables should be of potential use in preventing some hitherto elusive suicides, while the search for other unknown predictive factors is going on. On the other hand, the efficacy of prediction using these factors should be examined by further studies, preferably with a prospective design and in different cultural settings.
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Cheng et al. Acknowledgements This work was supported by the Committee on Research and Conference Grants (337/040/0001) and Medical Faculty Research Grant Fund (362-030-3384), University of Hong Kong.
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