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Original Article |

Absolute Risk of Suicide After First Hospital Contact in Mental Disorder FREE

Merete Nordentoft, MD; Preben Bo Mortensen, MD; Carsten Bøcker Pedersen, MD
[+] Author Affiliations

Author Affiliations: Psychiatric Centre Copenhagen, Mental Health Services, Capital Region of Denmark, and Faculty of Health Sciences, Copenhagen University, Copenhagen, Denmark (Dr Nordentoft); and National Centre for Register-Based Research, University of Aarhus, Aarhus, Denmark (Drs Mortensen and Pedersen).


Arch Gen Psychiatry. 2011;68(10):1058-1064. doi:10.1001/archgenpsychiatry.2011.113.
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Published online

Context Estimates of lifetime risk of suicide in mental disorders were based on selected samples with incomplete follow-up.

Objective To estimate, in a national cohort, the absolute risk of suicide within 36 years after the first psychiatric contact.

Design Prospective study of incident cases followed up for as long as 36 years. Median follow-up was 18 years.

Setting Individual data drawn from Danish longitudinal registers.

Participants A total of 176 347 persons born from January 1, 1955, through December 31, 1991, were followed up from their first contact with secondary mental health services after 15 years of age until death, emigration, disappearance, or the end of 2006. For each participant, 5 matched control individuals were included.

Main Outcome Measures Absolute risk of suicide in percentage of individuals up to 36 years after the first contact.

Results Among men, the absolute risk of suicide (95% confidence interval [CI]) was highest for bipolar disorder, (7.77%; 6.01%-10.05%), followed by unipolar affective disorder (6.67%; 5.72%-7.78%) and schizophrenia (6.55%; 5.85%-7.34%). Among women, the highest risk was found among women with schizophrenia (4.91%; 95% CI, 4.03%-5.98%), followed by bipolar disorder (4.78%; 3.48%-6.56%). In the nonpsychiatric population, the risk was 0.72% (95% CI, 0.61%-0.86%) for men and 0.26% (0.20%-0.35%) for women. Comorbid substance abuse and comorbid unipolar affective disorder significantly increased the risk. The co-occurrence of deliberate self-harm increased the risk approximately 2-fold. Men with bipolar disorder and deliberate self-harm had the highest risk (17.08%; 95% CI, 11.19%-26.07%).

Conclusions This is the first analysis of the absolute risk of suicide in a total national cohort of individuals followed up from the first psychiatric contact, and it represents, to our knowledge, the hitherto largest sample with the longest and most complete follow-up. Our estimates are lower than those most often cited, but they are still substantial and indicate the continuous need for prevention of suicide among people with mental disorders.

Figures in this Article

All mental disorders are associated with increased risk of suicide,16 and this risk is often reported as the increased relative risk or odds ratio for death by suicide by people with mental disorders who have contact with health services compared with those who do not. The absolute risk of death by suicide, often mentioned as lifetime risk of suicide after the onset of mental disorders, can be estimated as the percentage of a cohort expected to die by suicide before extinction. Although no studies have actually conducted lifetime follow-up, lifetime risk is mentioned in many scientific papers7,8 and textbooks.9 It has been estimated to be high, but these estimates have never previously been based on a large national sample with a prospective long-term follow-up. One of the most cited reports is the 1977 review conducted by Miles.7 This review estimated that 15% of persons affected with unipolar affective disorder would die by suicide, as well as 15% of persons with alcoholism and 10% of persons with schizophrenia. However, this review was based on rather small studies with selected samples and a rather short follow-up, and several authors later concluded that, for different reasons, Miles' estimates were most likely too high.1014 Later meta-analyses,1214 based on more sophisticated statistical methods and including some large long-term follow-up studies, found clearly lower figures. Inskip et al14 estimated the lifetime risk to be 6% for affective disorder, 7% for alcohol dependence, and 4% for schizophrenia. Bostwick and Pankratz12 estimated the risk to be 4% for patients hospitalized for affective disorders and 8.6% for those hospitalized for affective disorder and suicidality. Palmer et al13 estimated the lifetime risk to be 5.6% for schizophrenia. Recently, Dutta et al5 estimated the lifetime risk of suicide to be 3.23% for patients 20 years after the first psychotic diagnosis.

Although the lifetime risk of suicide has been reported in many studies, most estimates were based on incomplete follow-up in selected samples or were based on rather short-term follow-up of patients with first-time treated mental disorders. In addition, the lifetime morbid risk is not well defined from an epidemiological viewpoint. We will estimate the absolute risk of committing suicide within 36 years after the first onset of the disorder, using competing risks Cox regression to account for censoring emigration and death from other causes. Omitting such censoring will bias the estimated cumulative incidences upward. By using competing risks survival analyses,15 the absolute risks of suicide (or cumulative incidences) can be calculated as the percentages of persons in the population who had committed suicide at a given time since onset of the disorder of interest, taking into account that people may migrate or die of other causes.

For any dynamic population, the cumulative incidence of suicide is the best possible estimate of long-term absolute risk of suicide. We were able to use the unique Danish registers to estimate absolute cumulative risk of suicide for different mental disorders and to include a complete national sample of persons born after 1955 with follow-up to 51 years of age.

STUDY POPULATION

The Danish Civil Registration System16 was established in 1968, and all persons who are alive and living in Denmark are registered. Among many other variables, it includes information on personal identification number, sex, and date of birth; continuously updated information on vital status; and the personal identification number of parents. The personal identification number is used in all national registers, which enables accurate linkage between registers. Our study population included all persons born in Denmark from January 1, 1955, through December 31, 1991 (2.46 million people). A cohort of 176 347 persons who came into contact with secondary mental health services for the first time and 881 735 controls without any contact with mental health services were followed up prospectively for a maximum of 36 years, from 15 years through as old as 51 years (median follow-up, 18 years).

ASSESSMENT OF SUICIDE AND MENTAL ILLNESS

The study population was linked with the Danish Registers of Causes of Death17 to obtain information about any history of suicide (codes 950-959 from the International Statistical Classification of Diseases, 8th Revision [ICD-8 ], or codes X60-X84 from the International Statistical Classification of Diseases, 10th Revision [ICD-10 ]) and date of suicide, if any. The registry contains information for all residents who died in Denmark from 1970 through 2006. In Denmark, the legal regulation of death certification states that any case of sudden and unexpected death shall be reported to the police, and the death certificate may only be issued after a medicolegal examination.

The study population was also linked with the Danish Psychiatric Central Register18 to obtain information about mental illness. The Danish Psychiatric Central Register was computerized in 1969 and contains data on all admissions to Danish psychiatric inpatient facilities; from 1995, information on outpatient visits to psychiatric departments was included in the register. The register currently includes data on approximately 630 000 persons and 2.7 million contacts. From 1969 through 1993, the diagnostic system used was the Danish modification of the ICD-8,19 and from 1994, the ICD-10.20 Cohort members were categorized with a history of schizophrenia (ICD-8 code 295 or ICD-10 code F20), schizophrenialike psychoses (ICD-8 codes 297, 298.39, and 301.83 or ICD-10 codes F21-F29), bipolar affective disorder (ICD-8 codes 296.19 and 296.39 or ICD-10 codes F30 and F31), unipolar affective disorder (ICD-8 codes 296.09, 296.29, 296.89, 296.99, 298.09, 298.19, 300.49, and 301.19 or ICD-10 codes F32-F34, F38, and F39), substance abuse (ICD-8 codes 291, 294.30, 294.38, 303, and 304 or ICD-10 codes F10-F19), anorectic disorder (ICD-8 code 306.50 or ICD-10 code F50.0), and any mental illness (any ICD-8 or ICD-10 code) if they had been admitted to a psychiatric hospital or had been in outpatient care with one of these diagnoses. For each mental disorder, the date of onset was defined as the first day of the first contact (inpatient or outpatient) with the diagnosis of interest. The National Hospital Register was established in 1977, and information about all admissions to public hospitals in Denmark was prospectively recorded. Since 1995, outpatient visits were also registered. Because some patients with substance abuse disorders are treated only in somatic departments, we decided to include patients in the National Hospital Register21 who had a diagnosis of substance use disorders (ICD-8 codes 291, 294.30, 294.38, 303, and 304 or ICD-10 codes F10-F19).

Identifying deliberate self-harm in Danish registers is rather complicated because procedures have changed, and some procedures are not well complied with. We have identified deliberate self-harm in the different periods with different algorithms. From 1977 to 1986, deliberate self-harm was identified as persons with the diagnoses classified in ICD-8 codes E9500 through E9599 in the National Hospital Register or Danish Psychiatric Central Register. From 1987 to 1993, deliberate self-harm was identified as persons admitted with a“reason for contact code” of 4 in the National Hospital Register. After 1994, suicide attempts were identified as people fulfilling at least 1 of the following criteria in the National Hospital Register or Danish Psychiatric Central Register:

  1. Reason for contact code of 4;

  2. Any psychiatric diagnosis (ICD-10 chapter F) and a comorbid diagnosis of poisoning with medication and biological compounds (ICD-10 codes T36 through T50) or nonmedical compounds, excluding alcohol and poisoning from food (T52 through T60);

  3. Any psychiatric disorder (ICD-10 chapter F) and comorbid diagnosis reflecting lesions on the forearm, wrist, or hand (ICD-10 codes S51, S55, S59, S61, S65, or S69);

  4. Any contact with a hospital because of poisoning with weak or strong analgesics, hypnotics, sedatives, psychoactive drugs, antiepileptics, and antiparkinsonian drugs or carbon monoxide (ICD-10 codes T39, T42, T43, and T58); and

  5. Any somatic or psychiatric diagnosis X60 through X84.

The classification of deliberate self-harm was identical to that used previously.22,23

Analyses of deliberate self-harm were only possible beginning in 1977; therefore, the follow-up for these analyses is no longer than 30 complete years.

STUDY DESIGN AND STATISTICAL ANALYSIS

For each mental disorder, cohort members were followed up from their first hospital contact as inpatients or outpatients after 15 years of age until suicide, death from other causes, emigration from Denmark, disappearance, or December 31, 2006 (whichever came first). Because we aimed to study suicidal behavior among adolescents, we excluded from the analyses individuals who had their psychiatric disorder before 15 years of age. By selecting only persons born in 1955 and later, we ensured that the cohort consisted of incident cases, as the number of persons who had their first hospital contact owing to one of the mental disorders of interest before 15 years of age is very small.24

Competing risks survival analyses15 allowed us to calculate the absolute risks of suicide (or cumulative incidences) as the percentages of persons in the population who had committed suicide at a given time since the onset of the disorder of interest, taking into account that people may migrate or die of other causes. These analyses were made for each sex and were subdivided according to the age at onset of the disorder of interest. In this report, our interest is the probability of suicide. This probability, also referred to as the cumulative incidence, is not a simple function of the incidence rate of suicide; rather, it is estimated as the weighted integral of the incidence rates, in which the weights equal the survival function. In this situation, people born in 1955 contribute to the estimation of the incidence rate from time 0 to time 36, whereas people born in 1991 only contribute to the estimation of the incidence rate until 1 year after the first psychiatric contact. Additional details can be found in Rosthøj et al.25

To estimate the cumulative incidence of suicide among people with no history of mental illness, we adopted a slightly alternative strategy. For each person with a history of any mental illness (as defined in the“Assessment of Suicide and Mental Illness” subsection), we randomly selected 5 people of the same sex and same birth date who had no history of mental illness (time matched). Using the described strategy, we followed up this healthy population (881 735 persons) to provide absolute suicide risks. Because this healthy population was selected at random among all 2.46 million people included in the study population, the estimates obtained represent the absolute risk of suicide among all 2.46 million people without a mental disorder.

In addition, we performed analyses of comorbidity. Patients who had a diagnosis of substance abuse disorder plus any other mental disorder—at the same time or at different times—underwent separate analyses. Similarly, we performed analyses of comorbidity for patients with unipolar affective disorder in combination with other psychiatric disorders and any history of hospital treatment after deliberate self-harm. This study was approved by the Danish Data Protection Agency.

The absolute risk of suicide according to diagnostic group is shown in Table 1. Among men, suicide risk was highest in bipolar disorder (7.77%; 95% confidence interval [CI], 6.01%-10.05%), followed by unipolar affective disorder (6.67%; 5.72%-7.78%), schizophrenia (6.55%; 5.85%-7.34%), schizophrenialike disorders (5.90%; 5.21%-6.67%), and substance abuse treated in a psychiatric department (4.71%; 4.24%-5.23%). Among women, the highest risk was found among women with schizophrenia (4.91%; 95% CI, 4.03%-5.98%), followed by bipolar disorder (4.78%; 3.48%-6.56%), schizophrenialike disorder (4.07%; 3.28%-5.04%), unipolar affective disorder (3.77%; 3.05%-4.66%), substance abuse treated in a psychiatric department (3.34%; 2.80%-3.98%), and anorexia (2.62%; 1.08%-6.38%). In the nonpsychiatric population, the risk was 0.72% (95% CI, 0.61%-0.86%) for men and 0.26% (0.20%-0.35%) for women. The estimate of the suicide risk for men with anorexia is based on small numbers of cases.

Table Graphic Jump LocationTable 1. Cumulative Incidence of Suicide Up to 36 Years After First Psychiatric Contacta

The cumulative incidence of suicide by time since the first psychiatric contact for each of the disorders investigated is shown in the Figure for men and women. The steepest increase in suicide incidence occurs during the first years after first contact. The cumulative incidences of suicide were virtually independent of age at onset of the different mental disorders (data not shown).

Place holder to copy figure label and caption
Graphic Jump Location

Figure. Cumulative incidence of suicide by time since the first psychiatric contact among men (A) and women (B).

In Table 2, the cumulative incidence of suicide is presented for patients who had a diagnosis of a substance abuse disorder and a different additional mental disorders during the same contact or at different times. In all diagnostic groups, comorbidity with substance abuse disorder increased the cumulative incidence of suicide except among men with schizophrenia. In Table 3, the cumulative incidence of suicide is presented for patients who had a diagnosis of a unipolar affective disorder and a different additional mental disorder. For all mental disorders, comorbid occurrence of unipolar affective disorder increased the cumulative incidence of suicide.

Table Graphic Jump LocationTable 2. Cumulative Incidence of Suicide Up to 36 Years After the First Psychiatric Contact Among Individuals With Comorbid Substance Abusea
Table Graphic Jump LocationTable 3. Cumulative Incidence of Suicide Up to 36 Years After the First Psychiatric Contact Among Individuals With Comorbid Unipolar Affective Disordera

In Table 4, the cumulative incidence for patients who had attempted suicide at least once is presented in different diagnostic groups among men and women. Overall, across all diagnostic groups, deliberate self-harm doubled the risk. The highest cumulative incidence of suicide was found among men with bipolar disorder and deliberate self-harm (17.08%; 95% CI, 11.19%-26.07%).

Table Graphic Jump LocationTable 4. Cumulative Incidence of Suicide Up to 36 Years After the First Psychiatric Contact Among Individuals Admitted After Deliberate Self-harma

To our knowledge, this study has the hitherto largest sample and includes a long-term follow-up of a complete national sample from 15 to 51 years of age. We found the absolute risk of suicide in different psychiatric disorders to vary from 2% to 8%, higher for men than for women and highest for men and women with bipolar disorder, unipolar affective disorder, schizophrenia, and schizophrenialike disorder. For both sexes, comorbid occurrence of substance abuse and unipolar affective disorders increased the absolute suicide risk, and co-occurrence of deliberate self-harm generally doubled the risk in each diagnostic group. The suicide risk increased steeply during the first few years after first contact with psychiatric services.

Although the absolute suicide risks identified in this study are high, they are clearly lower than the often-cited figures reported by Guze and Robins8 and Miles.7 References to those old, exaggerated estimates should be replaced by more recent and correct ones. Estimates of the cumulative incidences in the literature have often ignored the fact that people may emigrate or die of other causes.

The strengths of this study are the large and representative number of cases investigated, the long follow-up, and the fact that we accounted for emigration and death from other causes. Omitting such censoring in our sample would bias the absolute risks upward by approximately 10%.15,25

The findings in our study are in agreement with the meta-analysis performed by Bostwick and Pankratz12 and Palmer et al,13 partly because Danish register-based studies contributed a large proportion of the patients and person-years included in their analyses. Our study population includes all the Danish patients included in the meta-analyses; in our study, they were followed up longer than in previous studies.

There are some limitations in a register-based study compared with a population-based survey. The study population includes only persons who have received some kind of treatment in psychiatric treatment facilities, and outpatient treatment was recorded only since 1995. However, most other studies have the same limitations.

Another limitation is that we were able to identify incident cases of mental illness only among people born in 1955 or later and to follow up these individuals until 2006, that is, people who had received a diagnosis of a mental illness before 51 years of age. We can only speculate whether the absolute risks reported are applicable to people with later onset of a mental disorder.

Based on our material, we cannot estimate lifetime risk because the cohort was followed up until, at most, 51 years of age. Also, because the design of the study exploits the advantages of including the longest possible historical period, there is a risk that changes in suicide risk occurred during the period investigated. Prior investigations have previously demonstrated that suicide rates for patients with schizophrenia,26 affective disorder, and substance abuse27 decreased and can be influenced by a range of conditions related to the treatment, as well as to other factors, such as availability of dangerous means.

The number of persons with bipolar disorder in our sample is much lower than the number of cases of schizophrenia. The explanation for the smaller figures is that many cases classified as bipolar II disorder in DSM terms will not be classified as bipolar disorders in ICD-8 and ICD-10 and also that the incidence of bipolar disorder peaks at a later age28 compared with schizophrenia.29 In the present, rather young cohort, some individuals have not yet developed bipolar disorder.

All persons in this study were classified according to the clinical diagnosis given at first contact with mental health services after 15 years of age. Diagnostic switch between, for instance, schizophrenialike disorder and schizophrenia or a switch between unipolar affective disorder and bipolar disorder is therefore not taken into account. Theoretically, persons who later switched from one group to another could have a different risk than those who remained in the same group, thereby artificially leveling out differences between diagnostic groups. However, diagnostic switch cannot be taken into account without introducing survival bias (healthy- worker effect).

Large prospective studies of first-onset cases with a long follow-up, such as the present study and the recent British 40-year follow-up of first-episode psychosis cases,30 provide good estimates of suicide risk. However, an inherent problem with such studies is that, by the time the results become available, the risk for new patients with first-episode psychosis may have changed because of changes in treatment and other factors.31 Since 2000, suicide rates in Denmark have been clearly lower than those in the previous decades, when many of the cases in the cohort died.31

We did find higher figures than Dutta et al5,30 in their study of patients with first-episode psychosis, which can be partly explained by differences between the 2 countries in classification of suicide, with higher suicide rates in Denmark.32 Other possible explanations are the higher proportion of outpatients in the British sample, differences in determination of cause of death, differences in access to data on previous treatment, or differences in the completeness of follow-up due to the Danish unique nationwide personal identifier, which ensures the most optimal conditions for selecting a true first-time-treated population and a complete follow-up. It is a limitation that the data are only available from Denmark, which might limit generalization of our findings to other countries. In the 1980s, Denmark had extraordinarily high suicide rates, most likely because of a large number of suicides with barbiturates.33 Because some suicides in this study occurred during that period, these figures might not reflect conditions in other countries.

Despite these limitations, it is beyond doubt that the risk of suicide is high in all the investigated mental disorders, and suicide preventive measures should be a mandatory part of treatment programs, not only for affective disorders but also for schizophrenia and related disorders, for substance abuse, and for anorexia.34 It is also evident that a history of deliberate self-harm markedly increases the risk of suicide across all diagnostic groups. In addition, as underlined in recent findings from a large Swedish study,35 attempted suicide should be considered a very important risk factor among patients with different mental disorders.

The fact that the steepest increase in suicide risk occurs during the initial years after first contact with mental health services can serve as an argument for intensive early-intervention services. By establishing closer contact and closer monitoring of symptoms, we hope that such services can reduce suicide risk in this high-risk period and thereby ensure that the long-term risk of suicide may be influenced positively.

Correspondence: Merete Nordentoft, MD, Psychiatric Centre Copenhagen, Bispebjerg Bakke 23, 2400 Copenhagen NV, Denmark (mn@dadlnet.dk).

Submitted for Publication: January 24, 2011; final revision received April 10, 2011; accepted May 20, 2011.

Author Contributions: All authors had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Financial Disclosure: None reported.

Funding/Support: This study was supported in part by the Stanley Medical Research Institute (Drs Mortensen and Pedersen).

Role of the Sponsors: The funding organization had no influence on the design or conduct of the study.

Mortensen PB, Agerbo E, Erikson T, Qin P, Westergaard-Nielsen N. Psychiatric illness and risk factors for suicide in Denmark.  Lancet. 2000;355(9197):9-12
PubMed   |  Link to Article
Qin P, Nordentoft M. Suicide risk in relation to psychiatric hospitalization: evidence based on longitudinal registers.  Arch Gen Psychiatry. 2005;62(4):427-432
PubMed   |  Link to Article
Harris EC, Barraclough B. Suicide as an outcome for mental disorders: a meta-analysis.  Br J Psychiatry. 1997;170:205-228
PubMed   |  Link to Article
Lönnqvist JK, Henriksson MM, Isometsä ET, Marttunen MJ, Heikkinen ME, Aro HM, Kuoppasalmi KI. Mental disorders and suicide prevention.  Psychiatry Clin Neurosci. 1995;49:(suppl 1)  S111-S116
PubMed   |  Link to Article
Dutta R, Murray RM, Hotopf M, Allardyce J, Jones PB, Boydell J. Reassessing the long-term risk of suicide after a first episode of psychosis.  Arch Gen Psychiatry. 2010;67(12):1230-1237
PubMed   |  Link to Article
Caldwell CB, Gottesman II. Schizophrenics kill themselves too: a review of risk factors for suicide.  Schizophr Bull. 1990;16(4):571-589
PubMed
Miles CP. Conditions predisposing to suicide: a review.  J Nerv Ment Dis. 1977;164(4):231-246
PubMed   |  Link to Article
Guze SB, Robins E. Suicide and primary affective disorders.  Br J Psychiatry. 1970;117(539):437-438
PubMed   |  Link to Article
Goodwin FK, Jamison KR. Manic-Depressive Illness: Bipolar Disorders and Recurrent Depression2nd ed. New York, NY: Oxford University Press; 2007
Blair-West GW, Mellsop GW, Eyeson-Annan ML. Down-rating lifetime suicide risk in major depression.  Acta Psychiatr Scand. 1997;95(3):259-263
PubMed   |  Link to Article
Blair-West GW, Cantor CH, Mellsop GW, Eyeson-Annan ML. Lifetime suicide risk in major depression: sex and age determinants.  J Affect Disord. 1999;55(2-3):171-178
PubMed   |  Link to Article
Bostwick JM, Pankratz VS. Affective disorders and suicide risk: a reexamination.  Am J Psychiatry. 2000;157(12):1925-1932
PubMed   |  Link to Article
Palmer BA, Pankratz VS, Bostwick JM. The lifetime risk of suicide in schizophrenia: a reexamination.  Arch Gen Psychiatry. 2005;62(3):247-253
PubMed   |  Link to Article
Inskip HM, Harris EC, Barraclough B. Lifetime risk of suicide for affective disorder, alcoholism and schizophrenia.  Br J Psychiatry. 1998;172:35-37
PubMed   |  Link to Article
Andersen PK, Borgan Ø, Gill RD, Keiding N. Statistical Models Based on Counting Processes. Corrected ed. New York, NY: Springer-Verlag; 1997
Pedersen CB, Gøtzsche H, Møller JO, Mortensen PB. The Danish Civil Registration System: a cohort of eight million persons.  Dan Med Bull. 2006;53(4):441-449
PubMed
Juel K, Helweg-Larsen K. The Danish Registers of Causes of Death.  Dan Med Bull. 1999;46(4):354-357
PubMed
Munk-Jørgensen P, Mortensen PB. The Danish Psychiatric Central Register.  Dan Med Bull. 1997;44(1):82-84
PubMed
World Health Organization.  Classification of Diseases: Extended Danish-Latin Version of the World Health Organization International Classification of Diseases, 8th Revision.  Copenhagen: Danish National Board of Health; 1971
World Health Organization.  WHO ICD-10Mental and Behavioural Disorders: Classification and Diagnostic Criteria [in Danish]. Copenhagen: Munksgaard Danmark; 1994
Andersen TF, Madsen M, Jørgensen J, Mellemkjoer L, Olsen JH. The Danish National Hospital Register: a valuable source of data for modern health sciences.  Dan Med Bull. 1999;46(3):263-268
PubMed
Qin P, Mortensen PB, Pedersen CB. Frequent change of residence and risk of attempted and completed suicide among children and adolescents.  Arch Gen Psychiatry. 2009;66(6):628-632
PubMed   |  Link to Article
Christiansen E, Goldney RD, Beautrai AL, Agerbo E. Youth suicide attempts and the dose-response relationship to parental risk factors: a population-based study.  Psychol Med. 2011;41(2):313-319
PubMed   |  Link to Article
Pedersen CB. No evidence of time trends in the urban-rural differences in schizophrenia risk among five million people born in Denmark from 1910 to 1986.  Psychol Med. 2006;36(2):211-219
PubMed   |  Link to Article
Rosthøj S, Andersen PK, Abildstrom SZ. SAS macros for estimation of the cumulative incidence functions based on a Cox regression model for competing risks survival data.  Comput Methods Programs Biomed. 2004;74(1):69-75
PubMed   |  Link to Article
Nordentoft M, Laursen TM, Agerbo E, Qin P, Høyer EH, Mortensen PB. Change in suicide rates for patients with schizophrenia in Denmark, 1981-97: nested case-control study.  BMJ. 2004;329(7460):261-266
PubMed   |  Link to Article
Qin P, Nordentoft M, Høyer EH, Agerbo E, Laursen TM, Mortensen PB. Trends in suicide risk associated with hospitalized psychiatric illness: a case-control study based on Danish longitudinal registers.  J Clin Psychiatry. 2006;67(12):1936-1941
PubMed   |  Link to Article
Laursen TM, Munk-Olsen T, Nordentoft M, Mortensen PB. A comparison of selected risk factors for unipolar depressive disorder, bipolar affective disorder, schizoaffective disorder, and schizophrenia from a Danish population-based cohort.  J Clin Psychiatry. 2007;68(11):1673-1681
PubMed   |  Link to Article
Thorup A, Waltoft BL, Pedersen CB, Mortensen PB, Nordentoft M. Young males have a higher risk of developing schizophrenia: a Danish register study.  Psychol Med. 2007;37(4):479-484
PubMed   |  Link to Article
Dutta R, Murray RM, Allardyce J, Jones PB, Boydell J. Early risk factors for suicide in an epidemiological first episode psychosis cohort.  Schizophr Res. 2011;126(1-3):11-19
PubMed   |  Link to Article
Nordentoft M. Prevention of suicide and attempted suicide in Denmark: epidemiological studies of suicide and intervention studies in selected risk groups.  Dan Med Bull. 2007;54(4):306-369
PubMed
Atkinson MW, Kessel N, Dalgaard JB. The comparability of suicide rates.  Br J Psychiatry. 1975;127:247-256
PubMed   |  Link to Article
Nordentoft M, Qin P, Helweg-Larsen K, Juel K. Restrictions in means for suicide: an effective tool in preventing suicide: the Danish experience.  Suicide Life Threat Behav. 2007;37(6):688-697
PubMed   |  Link to Article
Hawton K, Saunders KE. Psychiatric service development and suicide.  Lancet. 2009;373(9658):99-100
PubMed   |  Link to Article
Runeson B, Tidemalm D, Dahlin M, Lichtenstein P, Långström N. Method of attempted suicide as predictor of subsequent successful suicide: national long term cohort study.  BMJ. 2010;341:c3222
PubMed  |  Link to Article   |  Link to Article

Figures

Place holder to copy figure label and caption
Graphic Jump Location

Figure. Cumulative incidence of suicide by time since the first psychiatric contact among men (A) and women (B).

Tables

Table Graphic Jump LocationTable 1. Cumulative Incidence of Suicide Up to 36 Years After First Psychiatric Contacta
Table Graphic Jump LocationTable 2. Cumulative Incidence of Suicide Up to 36 Years After the First Psychiatric Contact Among Individuals With Comorbid Substance Abusea
Table Graphic Jump LocationTable 3. Cumulative Incidence of Suicide Up to 36 Years After the First Psychiatric Contact Among Individuals With Comorbid Unipolar Affective Disordera
Table Graphic Jump LocationTable 4. Cumulative Incidence of Suicide Up to 36 Years After the First Psychiatric Contact Among Individuals Admitted After Deliberate Self-harma

References

Mortensen PB, Agerbo E, Erikson T, Qin P, Westergaard-Nielsen N. Psychiatric illness and risk factors for suicide in Denmark.  Lancet. 2000;355(9197):9-12
PubMed   |  Link to Article
Qin P, Nordentoft M. Suicide risk in relation to psychiatric hospitalization: evidence based on longitudinal registers.  Arch Gen Psychiatry. 2005;62(4):427-432
PubMed   |  Link to Article
Harris EC, Barraclough B. Suicide as an outcome for mental disorders: a meta-analysis.  Br J Psychiatry. 1997;170:205-228
PubMed   |  Link to Article
Lönnqvist JK, Henriksson MM, Isometsä ET, Marttunen MJ, Heikkinen ME, Aro HM, Kuoppasalmi KI. Mental disorders and suicide prevention.  Psychiatry Clin Neurosci. 1995;49:(suppl 1)  S111-S116
PubMed   |  Link to Article
Dutta R, Murray RM, Hotopf M, Allardyce J, Jones PB, Boydell J. Reassessing the long-term risk of suicide after a first episode of psychosis.  Arch Gen Psychiatry. 2010;67(12):1230-1237
PubMed   |  Link to Article
Caldwell CB, Gottesman II. Schizophrenics kill themselves too: a review of risk factors for suicide.  Schizophr Bull. 1990;16(4):571-589
PubMed
Miles CP. Conditions predisposing to suicide: a review.  J Nerv Ment Dis. 1977;164(4):231-246
PubMed   |  Link to Article
Guze SB, Robins E. Suicide and primary affective disorders.  Br J Psychiatry. 1970;117(539):437-438
PubMed   |  Link to Article
Goodwin FK, Jamison KR. Manic-Depressive Illness: Bipolar Disorders and Recurrent Depression2nd ed. New York, NY: Oxford University Press; 2007
Blair-West GW, Mellsop GW, Eyeson-Annan ML. Down-rating lifetime suicide risk in major depression.  Acta Psychiatr Scand. 1997;95(3):259-263
PubMed   |  Link to Article
Blair-West GW, Cantor CH, Mellsop GW, Eyeson-Annan ML. Lifetime suicide risk in major depression: sex and age determinants.  J Affect Disord. 1999;55(2-3):171-178
PubMed   |  Link to Article
Bostwick JM, Pankratz VS. Affective disorders and suicide risk: a reexamination.  Am J Psychiatry. 2000;157(12):1925-1932
PubMed   |  Link to Article
Palmer BA, Pankratz VS, Bostwick JM. The lifetime risk of suicide in schizophrenia: a reexamination.  Arch Gen Psychiatry. 2005;62(3):247-253
PubMed   |  Link to Article
Inskip HM, Harris EC, Barraclough B. Lifetime risk of suicide for affective disorder, alcoholism and schizophrenia.  Br J Psychiatry. 1998;172:35-37
PubMed   |  Link to Article
Andersen PK, Borgan Ø, Gill RD, Keiding N. Statistical Models Based on Counting Processes. Corrected ed. New York, NY: Springer-Verlag; 1997
Pedersen CB, Gøtzsche H, Møller JO, Mortensen PB. The Danish Civil Registration System: a cohort of eight million persons.  Dan Med Bull. 2006;53(4):441-449
PubMed
Juel K, Helweg-Larsen K. The Danish Registers of Causes of Death.  Dan Med Bull. 1999;46(4):354-357
PubMed
Munk-Jørgensen P, Mortensen PB. The Danish Psychiatric Central Register.  Dan Med Bull. 1997;44(1):82-84
PubMed
World Health Organization.  Classification of Diseases: Extended Danish-Latin Version of the World Health Organization International Classification of Diseases, 8th Revision.  Copenhagen: Danish National Board of Health; 1971
World Health Organization.  WHO ICD-10Mental and Behavioural Disorders: Classification and Diagnostic Criteria [in Danish]. Copenhagen: Munksgaard Danmark; 1994
Andersen TF, Madsen M, Jørgensen J, Mellemkjoer L, Olsen JH. The Danish National Hospital Register: a valuable source of data for modern health sciences.  Dan Med Bull. 1999;46(3):263-268
PubMed
Qin P, Mortensen PB, Pedersen CB. Frequent change of residence and risk of attempted and completed suicide among children and adolescents.  Arch Gen Psychiatry. 2009;66(6):628-632
PubMed   |  Link to Article
Christiansen E, Goldney RD, Beautrai AL, Agerbo E. Youth suicide attempts and the dose-response relationship to parental risk factors: a population-based study.  Psychol Med. 2011;41(2):313-319
PubMed   |  Link to Article
Pedersen CB. No evidence of time trends in the urban-rural differences in schizophrenia risk among five million people born in Denmark from 1910 to 1986.  Psychol Med. 2006;36(2):211-219
PubMed   |  Link to Article
Rosthøj S, Andersen PK, Abildstrom SZ. SAS macros for estimation of the cumulative incidence functions based on a Cox regression model for competing risks survival data.  Comput Methods Programs Biomed. 2004;74(1):69-75
PubMed   |  Link to Article
Nordentoft M, Laursen TM, Agerbo E, Qin P, Høyer EH, Mortensen PB. Change in suicide rates for patients with schizophrenia in Denmark, 1981-97: nested case-control study.  BMJ. 2004;329(7460):261-266
PubMed   |  Link to Article
Qin P, Nordentoft M, Høyer EH, Agerbo E, Laursen TM, Mortensen PB. Trends in suicide risk associated with hospitalized psychiatric illness: a case-control study based on Danish longitudinal registers.  J Clin Psychiatry. 2006;67(12):1936-1941
PubMed   |  Link to Article
Laursen TM, Munk-Olsen T, Nordentoft M, Mortensen PB. A comparison of selected risk factors for unipolar depressive disorder, bipolar affective disorder, schizoaffective disorder, and schizophrenia from a Danish population-based cohort.  J Clin Psychiatry. 2007;68(11):1673-1681
PubMed   |  Link to Article
Thorup A, Waltoft BL, Pedersen CB, Mortensen PB, Nordentoft M. Young males have a higher risk of developing schizophrenia: a Danish register study.  Psychol Med. 2007;37(4):479-484
PubMed   |  Link to Article
Dutta R, Murray RM, Allardyce J, Jones PB, Boydell J. Early risk factors for suicide in an epidemiological first episode psychosis cohort.  Schizophr Res. 2011;126(1-3):11-19
PubMed   |  Link to Article
Nordentoft M. Prevention of suicide and attempted suicide in Denmark: epidemiological studies of suicide and intervention studies in selected risk groups.  Dan Med Bull. 2007;54(4):306-369
PubMed
Atkinson MW, Kessel N, Dalgaard JB. The comparability of suicide rates.  Br J Psychiatry. 1975;127:247-256
PubMed   |  Link to Article
Nordentoft M, Qin P, Helweg-Larsen K, Juel K. Restrictions in means for suicide: an effective tool in preventing suicide: the Danish experience.  Suicide Life Threat Behav. 2007;37(6):688-697
PubMed   |  Link to Article
Hawton K, Saunders KE. Psychiatric service development and suicide.  Lancet. 2009;373(9658):99-100
PubMed   |  Link to Article
Runeson B, Tidemalm D, Dahlin M, Lichtenstein P, Långström N. Method of attempted suicide as predictor of subsequent successful suicide: national long term cohort study.  BMJ. 2010;341:c3222
PubMed  |  Link to Article   |  Link to Article

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Effects of Sex and Comorbidity on Suicide Risk
Posted on February 1, 2012
Enrique Baca-Garcia, M.D., Ph.D.
Department of Psychiatry, College of Physicians and Surgeons, Columbia University, New York, NY,
Conflict of Interest: None Declared
The authors present some of their findings in a way that may be misleading. Specifically, they concluded that “For both sexes, comorbid occurrence of substance abuse and unipolar affective disorders increased the absolute suicide risk”. Upon careful examination, it appears that, strikingly, the presence of comorbid substance abuse does not significantly and uniformly increase suicide risk in all psychiatric disorders across sexes. The article used survival analysis to calculate the absolute risk of suicide. Since we do not have access to the survival data, we calculated approximate confidence intervals for the relative risk (RR) using a formula based on the group-wise absolute risks. We followed the example of the original article and did not adjust for multiple testing. We calculated the RR of suicide for three different exposures (comorbid substance abuse, comorbid unipolar affective disorder, and comorbid self- harm) using two comparison groups: individuals without a mental disorder, and individuals with the same psychiatric disorder without comorbidity.
We found significant increases in RR for suicide for all psychiatric disorders compared to the population without mental illness. Comorbid substance abuse, comorbid unipolar affective disorder and deliberate self- harm were all significantly associated with an increase in suicide risk for every disorder in both sexes, with the exception of males with schizophrenia and comorbid substance abuse. There were sex differences in the magnitude of the effect. While compared to men, women had significantly greater RR for suicide than the non- psychiatric population in all categories, except among women with both bipolar and unipolar lifetime diagnoses, when comparisons were made between those with comorbid disorders and psychiatric controls things looked different. For example, men had higher RR than women when substance abuse was present in the context of any psychiatric disorder and unipolar depression, but women with comorbid substance abuse and schizophrenia had a higher RR than men, compared to psychiatric controls. While women with both bipolar and unipolar lifetime diagnoses had higher RR than men, the opposite was true in schizophrenia comorbid with unipolar disorder. Deliberate self-harm appeared to increase risk across both sexes with a trend for a greater effect for men with schizophrenia, compared to psychiatric controls.
Two key take-home-messages can be derived from these findings. First, strikingly, and contrary to clinical lore as well as compared to what is observed in other conditions1-3 in males with schizophrenia, comorbid substance abuse does not further increase the risk for suicide. Second, there is a sex-differential effect of comorbid diagnoses on the risk for suicide, with the magnitude of risk differing across diagnoses. Notably, suicide risk associated with schizophrenia is increased by comorbid substance abuse for women and decreased by comorbid substance abuse for men.
This is consistent with reported sex-differences in the impact of comorbid conditions on suicide risk in psychiatric disorders.1 Why only males with schizophrenia are protected by the presence of comorbid substance abuse is not known. One possible explanation is that males with schizophrenia and comorbid SUD are more likely to die from other unnatural deaths besides suicide.1
REFERENCES
1. Yoon YH, Chen CM, Yi HY, Moss HB. Effect of comorbid alcohol and drug use disorders on premature death among unipolar and bipolar disorder decedents in the United States, 1999 to 2006. Compr Psychiatry. Sep-Oct 2011;52(5):453-464.
2. Hor K, Taylor M. Suicide and schizophrenia: a systematic review of rates and risk factors. J Psychopharmacol. Nov 2010;24(4 Suppl):81-90.
3. McGirr A, Tousignant M, Routhier D, et al. Risk factors for completed suicide in schizophrenia and other chronic psychotic disorders: a case- control study. Schizophr Res. May 2006;84(1):132-143.

Conflict of Interest: None declared
Authors reply
Posted on January 5, 2012
Merete Nordentoft, DMSc, phd, MPH
Psychiatric Centre Copenhagen, Copenhagen Universityhospital
Conflict of Interest: None Declared
We agree that based on the cumulative incidences reported it is possible to calculate relative risks, although we are unaware of the method used to approximate confidence intervals. However, the novelty of our paper was the ability to calculate absolute long-term risks of suicide (alias cumulative incidences) since these are much more informative for patients with mental illnesses and their relatives compared to relative risks. For example, based on our Table 1, women with schizophrenia had an 18.9-fold (=4.91/0.26) relative risk of suicide compared to mentally healthy women, whereas males with schizophrenia had only a 9.1-fold (=6.55/0.72) relative risk compared to mentally healthy males. However, when considering life-time risks males with schizophrenia had the highest absolute risk of suicide (Table 1: males: 6.55 percent; females: 4.91 percent). The strong contrast between these different measures of disease stems from the differences in life-time risks for people without mental disorders (Table 1: males: 0.72 percent; females: 0.26 percent). We also agree with Enrique Baca-Garcia et al that our statement in the comment that “For both sexes, comorbid occurrence of substance abuse and unipolar affective disorders increased the absolute suicide risk, and co- occurrence of deliberate self-harm generally doubled the risk in each diagnostic group.” was incorrect. The correct wording should have detailed that comorbidity with substance abuse did not increase suicide risk among males with schizophrenia. However, this was detailed in the result section along with the description on Table 2 (Page 1061, paragraph 1). We apologize for this inaccuracy. We do not agree with Enrique Baca-Garcia et al in their interpretation of substance abuse being protective for suicide among men with schizophrenia. The absolute risk of suicide among men with schizophrenia seems slightly higher (6.55 % [95 % C.I. 5.85 - 7.34]) than the corresponding figure for men with schizophrenia and comorbid substance abuse (5.88 % [95 % C.I. 4.90 - 7.04]), but the confidence intervals are overlapping. We agree with Enrique Baca-Garcia et al that our findings indicate that in men with schizophrenia, substance abuse does not add further to the risk of suicide. Merete Nordentoft, Preben Bo Mortensen and Carsten Pedersen
Conflict of Interest: None declared
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