© 2014 John Wiley & Sons A/S Published by John Wiley & Sons Ltd.

Bipolar Disorders 2014: 16: 732–740

BIPOLAR DISORDERS

Original Article

Suicide in bipolar disorder: characteristics and subgroups Schaffer A, Sinyor M, Reis C, Goldstein BI, Levitt AJ. Suicide in bipolar disorder: characteristics and subgroups. Bipolar Disord 2014: 16: 732–740. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd. Objectives: The development of more sophisticated models for understanding suicide among people with bipolar disorder (BD) requires diagnosis-specific data. The present study aimed to elucidate differences between people who die by suicide with and without BD, and to identify subgroups within those with BD. Methods: Data on all suicide deaths in the city of Toronto from 1998 to 2010 were extracted from the Office of the Chief Coroner of Ontario, including demographics, clinical variables, recent stressors, and details of the suicide. Comparisons of person- and suicide-specific variables between suicide deaths among those with BD (n = 170) and those without (n = 2,716) were conducted, and a cluster analysis was performed among the BD suicide group only. Results: Those in the BD suicide group were more likely than those in the non-BD suicide group to be female [odds ratio (OR) = 1.75, 95% confidence interval (CI): 1.27–2.42; p = 0.001], to have made a past suicide attempt (OR = 2.01, 95% CI: 1.45–2.80; p < 0.0001), and to have had recent contact with psychiatric or emergency services (OR = 1.59, 95% CI: 1.00–2.52; p = 0.049). Five clusters were identified within the BD group, with differences between clusters in age; sex; marital status; living circumstances; past suicide attempts; substance abuse; interpersonal, employment/financial, and legal/police stressors; and rates of death by fall/jump or self-poisoning. Conclusions: The present findings identified differences between BD and non-BD suicide groups, providing support to the utilization of an illnessspecific approach to better understanding suicide in BD. Subgroups of BD suicide deaths, if replicated, should also be incorporated into the design and analysis of future studies of suicide in BD.

Suicide is a complex behavioural endpoint resulting from a host of factors. One of the most important of these is mental illness, and understanding the role of specific diagnoses may be important for the development of more sophisticated models of understanding suicide (1). People with bipolar disorder (BD) are known to have among the highest rate of suicide compared to those with other mental disorders (2–15). BD is associated with an estimated rate of suicide deaths of 0.2 to 0.4 per 100 person-years (6, 16, 17), and a standardized mortality ratio of 10–30 times that

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Ayal Schaffera,b, Mark Sinyorb,c, Catherine Reisa, Benjamin I Goldsteind,e and Anthony J Levittb,c,f a

Mood and Anxiety Disorders Program, Department of Psychiatry, Sunnybrook Health Sciences Centre, bDepartment of Psychiatry, University of Toronto, cDepartment of Psychiatry, Sunnybrook Health Sciences Centre, d Department of Psychiatry, Centre for Youth Bipolar Disorder, Sunnybrook Health Sciences Centre, eDepartments of Psychiatry and Pharmacology, University of Toronto, fCentre for Mobile Computing in Mental Health, Sunnybrook Health Sciences Centre, Toronto, ON, Canada

doi: 10.1111/bdi.12219 Key words: bipolar disorder – cluster analysis – suicide Received 8 July 2013, revised and accepted for publication 12 November 2013 Corresponding author: Ayal Schaffer, M.D., F.R.C.P.C. Mood and Anxiety Disorders Program Department of Psychiatry Sunnybrook Health Sciences Centre 2075 Bayview Avenue, Room FG 52 Toronto, ON Canada, M4N 3M5 Fax: 416-480-4613 E-mail: [email protected]

of the general population (18, 19). Prospective BD cohort studies of variable duration report suicide occurring in 0.2–6.0% of people with the illness (5, 9, 13, 16, 17, 20–22), with the longer studies reporting a 3–6% risk. The urgent need for a better understanding of suicide in the context of BD is widely accepted (23), with an emerging consensus that a more diagnosis-specific approach is warranted to inform prevention strategies (24–28). Numerous risk factors for suicide or suicide attempts have been studied within BD, including

Suicide in bipolar disorder gender (8, 13, 15–17, 29), age (9, 12, 16), marital status (30), past suicide attempts (31–33), comorbidity (16, 21, 30, 34–40), and psychosocial stressors (30, 41, 42); however, there are limited data directly comparing these factors in a group of people identified as having BD and a non-BD group. This is an important line of inquiry that can identify key factors specific to BD. A Taiwanese study reported that among people who had died by suicide, people with BD were older than those with schizophrenia but younger than those with other psychiatric conditions (12). A recent large British study of suicide that included only those people seen in the mental health system during the year prior to death reported that, compared to non-BD suicide deaths, people with BD who died from suicide were younger, with a higher preponderance of females, lower likelihood of past self-harm, longer duration of illness, more contact with the mental health system, and higher rates of jumping as the method of suicide (43). This study, however, did not include suicides among people who had not had recent contact with the mental health system. Previous data suggested that over 50% of people who die by suicide do not make contact with mental health care services during the year prior to death; therefore, further information is needed to incorporate those with BD who die from suicide without having had recent contact with mental health services (44–49). Other studies of BD suicide deaths have also examined suicide-specific factors such as method of suicide (9, 12, 22, 50–54) and recent contact with psychiatric services (7, 50, 55), but few have compared findings in BD and non-BD suicide deaths. We are not aware of any study that has compared all BD and non-BD suicide deaths in a geographic area among a wide range of demographic, clinical, precipitating, and suicidespecific factors. Beyond the comparison with other groups, it is important to elucidate possible subgroups within BD suicide deaths. BD is a complex, heterogeneous illness that can occur throughout the lifespan. Amalgamating all diagnosis-specific suicides may limit our understanding of key subpopulations related to demographics, clinical factors, and precipitants. Logan et al. (56) reported the results of a clustering analysis of all suicide deaths in 12 US states, and identified nine different subgroups based on characteristics from each of these categories. A similar cluster analysis has not been reported among people with BD who have died from suicide. The goals of the present explorative study were, first, to compare the demographics, clinical vari-

ables, recent stressors, and suicide details among people with BD who died by suicide to those of a non-BD suicide group, and, second, to identify subgroups within the BD suicide group. Methods

Data were systematically extracted from charts of the Office of the Chief Coroner (OCC) of Ontario for all deaths in the city of Toronto, Ontario from 1998 to 2010 that were ruled as suicides according to a standard of a high degree of probability (57, 58). There is no gold standard method for coding a death as a suicide, but OCC reliability data are good in the presence of multiple factors contributing to suicide risk (e.g., 73–98% in the context of depression and at least one other factor such as prior suicide attempt or presence of a suicide note) (59). Coroner’s data validation studies have found that the risk of under-reporting suicide is greater than over-reporting, which supports the use of the coroner’s definition of a suicide death for the present study (59, 60). Information about suicide deaths that occurred after 2010 were not part of the study as it takes approximately two years for all OCC investigations to be completed. Each chart contained a coroner’s investigation report and pathology report with extensive information gathered by the OCC as part of the determination of the cause and particulars of the death. Additional information was collected by the OCC from transcripts of interviews with family, acquaintances, and physicians; letters from family members; police reports; hospital records; and copies of suicide notes when available. A standardized data extraction procedure was utilized to collect data on: (i) Demographics: age, gender, marital status, living circumstances (living with others or alone); (ii) Clinical variables: mental health diagnosis, substance abuse history (including alcohol, drugs, or both), known past suicide attempts, contact with psychiatric or emergency services in the week prior to death, comorbid medical conditions; (iii) Recent stressors: employment/financial, interpersonal stressor (conflict or relationship breakup), medical/health, police/legal, bereavement; (iv) Details of suicide: method (hanging, other asphyxia, drowning/ hypothermia, self-poisoning, jump/fall from height or subway/train/motor vehicle collision, cutting/stabbing, or shooting), location of death, presence of a suicide note. Two study investigators (MS and AS) provided onsite training to a research assistant and were then in continuous contact on a weekly basis to address any questions and reach consensus regarding coding for

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Schaffer et al. more complex charts. Demographic data and details of the suicide were available in 99% of coroner charts. Clinical and stressor variables were only included in the coroner charts if they were positive (e.g., an employment stressor was only coded if documented as present). This raises the possibility that an employment stressor may have been present but was not identified by the coroner. All clinical and stressor variables were therefore considered as estimates, with possible under-reporting. Further details on the full dataset of suicides have been published previously (61). The presence of a reported diagnosis of BD was established based on information in the coroner’s investigation report. Diagnostic information was obtained by the coroner from a variety of sources, including medical records from the decedent’s physician(s), collateral information from the family (e.g., a wife reporting that her husband had a longstanding history of BD), the police report of personal records or other evidence that was present at the scene of death or the home of the deceased, and the content of a suicide note stating a diagnosis of BD. Specific symptom criteria or psychological autopsies were not available. Based on the nature of the data collected, the accuracy of the diagnosis could not be verified, and the total number recorded is likely an under-estimation of the true number of BD suicides. All suicide deaths in people with a BD diagnosis documented as such in the coroner’s records were included in the sample of BD suicide deaths, and all other suicides were included in the sample of non-BD suicide deaths. The only exception was suicides in which both BD and schizophrenia/schizoaffective disorder were reported (n = 5), in which case we coded these as not having BD. The OCC granted approval to the present study and provided full access to their records. The study was approved by the Research Ethics Board at Sunnybrook Health Sciences Centre, Toronto, Canada. Strict privacy procedures utilized by the OCC were fully adhered to, with all extracted data maintained in an encrypted and de-identified format. Statistical analysis

Univariate analyses comparing the BD and nonBD suicides were conducted on all demographic, clinical, stressor, and suicide-specific variables described earlier. We used t-tests for continuous variables, and chi-square tests for categorical variables. In order to identify independent contributions to variance in the presence or absence of BD,

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logistic regression was completed with all variables entered that were different (at a level of p < 0.05) in the univariate analyses. A two-step cluster analysis was performed within the BD suicide group only, with clusters created by using categorical and continuous predictor variables suggested from previous research to be related to risk of suicide. Categorical variables that were present in < 10% of each cluster were removed and the cluster analysis completed again with the refined list of variables. A high degree of collinearity was present between marital status and living arrangements; therefore, one variable (marital status) was removed from the cluster analysis, but maintained in the subsequent descriptions of the clusters. Predictor variables retained in the final cluster analysis were: age, gender, living circumstances, past suicide attempt, substance abuse history (drug and/or alcohol), recent employment/financial stressor, interpersonal stressor, and police/legal stressor. The best model for cluster quality (Silhouette measure of cohesion and separation) resulted from separation into five clusters, with a ratio of sizes from largest cluster to smallest cluster of 2.43. The cluster analysis identified differences in predictor variable importance, and each cluster had a unique hierarchy of predictor variables that were most important for its creation. The five clusters were compared by univariate analyses of all demographic, clinical, stressor, and suicide-specific variables, irrespective of whether they were included in the formation of the clusters. Results

BD was recorded in 5.9% (170/2,886) of all suicide deaths in the city of Toronto from 1998 to 2010. The yearly percentage of BD suicide deaths as a proportion of all suicides varied from 3.1% to 7.3%, with no clear pattern emerging over time [v2(12) = 6.888, p = 0.865]. Table 1 shows the comparison of demographic, clinical, and stressor variables between the BD suicide group and nonBD suicide group. Univariate analyses revealed a number of differences; those in the BD suicide group were more likely than those in the non-BD suicide group to be female, were younger at the time of death, had higher rates of past suicide attempt, were more likely to have had contact with psychiatric or emergency services during the week prior to death, and were more likely to have had comorbid substance abuse, but lower rates of employment/financial or recent medical stressors. Logistic regression found independent contributions to variance within gender [female odds ratio

Suicide in bipolar disorder Table 1. Comparison of pre-death variables among bipolar disorder suicides and non-bipolar disorder suicides in Toronto, Canada, 1998–2010 BD versus non-BD Variables Gender, % male Age, years, mean (SD) Age categories, years, % ≤ 24 25–64 ≥ 65 Marital status, % married Living circumstances, % with others Past suicide attempts, % yes Psychiatry/ER visit in past week, % Comorbid substance abuse, %a Comorbid medical condition, % Recent stressors, % Bereavement Employment/financial Interpersonalb Recent health/medical Police/legal

BD (n = 170)

Non-BD (n = 2,716)

56.5 43.3 (13.5)

71.7 47.1 (17.8)

7.1 87.6 5.3 20.0 51.8 47.1 14.7 26.5 32.4 5.9 11.8 19.4 3.5 6.5

v2 or t-score

p-value

18.19 2.72 20.03

< 0.001 0.007 < 0.001

9.9 72.8 17.3 25.6 55.4 25.8 7.6 19.8 32.3

2.65 0.88 36.79 10.86 4.41 0.00

0.10 0.35 < 0.001 0.001 0.04 0.99

5.5 18.3 22.7 12.6 6.8

0.04 4.65 1.00 12.33 0.03

0.84 0.03 0.32 < 0.001 0.86

BD = bipolar disorder; ER = emergency room; SD = standard deviation. a Drug or alcohol. b Conflict or relationship breakup. Statistically significant p-values were bolded.

(OR) = 1.75, 95% confidence interval (CI): 1.27– 2.42; p = 0.001], past suicide attempts (OR = 2.01, 95% CI: 1.45–2.80; p < 0.0001), contact with psychiatric or emergency services (OR = 1.59, 95% CI: 1.00–2.52; p = 0.049), and recent medical

Table 2. Comparison of suicide-specific variables among bipolar disorder suicides and non-bipolar disorder suicides in Toronto, Canada, 1998–2010 BD versus non-BD

Variables, % Presence of a suicide note Suicide at home Suicide methoda Hanging Other asphyxia Drowning/ hypothermia Self-poisoning Fall/jump Shooting Cutting/stabbing

v2 or t-score

p-value

30.2

1.51

0.22

64.1

63.1

0.08

0.78

17.1 7.6 2.9

29.7 7.4 2.4

12.51 0.01 0.20

< 0.0001 0.94 0.65

33.5 30.0 2.4 2.9

17.4 32.0 5.0 3.3

27.71 0.30 2.44 0.07

< 0.0001 0.58 0.12 0.79

BD (n = 170)

Non-BD (n = 2,716)

34.7

BD = bipolar disorder. Specific methods that accounted for < 1% of either group were not included. Statistically significant p-values were bolded.

a

stressor (OR = 0.33, 95% CI: 0.14–0.76, p = 0.008). A comparison of suicide-specific variables between BD and non-BD suicide groups is shown in Table 2. Differences in method of suicide were identified, with higher rates of lethal self-poisoning and lower rates of hanging in the BD suicide group. Most BD self-poisoning deaths involved multiple lethal substances. Substances present at the time of death within the BD group included psychotropic medications (86.6%), alcohol (41.1%), and over-the-counter medications (37.5%). A cluster analysis of the BD suicide group was completed, with the best model achieved by separation into five clusters ranging in size from n = 56 (32.9%) to n = 23 (13.5%). The most important predictors in the cluster analysis model (in decreasing order of importance) were substance abuse, past suicide attempts, gender, living circumstances, employment/financial stressor, police/legal stressor, interpersonal stressor, and age. The results shown in Table 3 describe and compare these five clusters in terms of demographics, clinical variables, types of stressors prior to suicide, suicide method, location, and presence of a suicide note. Clusters were arbitrarily numbered from largest (Cluster 1) to smallest (Cluster 5). There were differences in nearly all pre-death variables, with the exceptions of broad age categories,

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Schaffer et al. Table 3. Characteristics of clusters of 170 bipolar disorder suicides in Toronto, Canada, 1998–2010

Variables Demographics Age, years, mean (SD) Age categories, years, % ≤ 24 25–64 ≥ 65 Gender, % male Marital status, % married Living circumstances, % with others Clinical, % Past suicide attempts, yes Substance abuse Medical condition Contact with psychiatry/ER services in past week Specific stressor in past year, % Interpersonal stressor Employment/financial Police/legal Bereavement Specific cause of death, % Hanging Fall/jump Self-poisoning Non-hanging asphyxia Firearm Cutting/stabbing Drowning/hypothermia Self-immolation Other suicide details, % Suicide note left Suicide occurred at home

Cluster 1 (n = 56)

42.5 (13.1)

Cluster 2 (n = 32)

Cluster 3 (n = 30)

Cluster 4 (n = 29)

Cluster 5 (n = 23)

F or v2 2.40a 8.6

df

p-value

4 8

0.05 0.38

41.7 (16.2)

49.6 (12.2)

43.4 (11.1)

39.4 (12.8)

8.9 87.5 3.6 100 14.3 42.9

9.4 81.2 9.4 46.9 34.4 93.8

0 90.0 10.0 36.7 3.3 0

3.4 93.1 3.4 48.3 20.7 44.8

13.0 87.0 0 0 34.8 91.3

79.8 13.6 71.5

4 4 4

< 0.0001 0.009 < 0.0001

0 28.6 26.8 12.5

100 0 31.2 21.9

66.7 0 46.7 20.0

79.3 100 41.4 13.8

21.7 0 17.4 4.3

108.4 111.3 7.1 4.2

4 4 4 4

Suicide in bipolar disorder: characteristics and subgroups.

The development of more sophisticated models for understanding suicide among people with bipolar disorder (BD) requires diagnosis-specific data. The p...
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