Review
Risk factors for suicide in individuals with depression: A systematic review

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Abstract

Background

Depression is the most common psychiatric disorder in people who die by suicide. Awareness of risk factors for suicide in depression is important for clinicians.

Methods

In a systematic review of the international literature we identified cohort and case-control studies of people with depression in which suicide was an outcome, and conducted meta-analyses of potential risk factors.

Results

Nineteen studies (28 publications) were included. Factors significantly associated with suicide were: male gender (OR=1.76, 95% CI=1.08–2.86), family history of psychiatric disorder (OR=1.41, 95% CI=1.00–1.97), previous attempted suicide (OR=4.84, 95% CI=3.26–7.20), more severe depression (OR=2.20, 95% CI=1.05–4.60), hopelessness (OR=2.20, 95% CI=1.49–3.23) and comorbid disorders, including anxiety (OR=1.59, 95% CI=1.03–2.45) and misuse of alcohol and drugs (OR=2.17, 95% CI=1.77–2.66).

Limitations

There were fewer studies than suspected. Interdependence between risk factors could not be examined.

Conclusions

The factors identified should be included in clinical assessment of risk in depressed patients. Further large-scale studies are required to identify other relevant factors.

Introduction

In most studies of people dying by suicide, approximately nine out of every ten individuals appear to have had a psychiatric disorder at the time of their death (Henriksson et al., 1993, Cavanagh et al., 2003). Psychological autopsy studies have shown that depression is the most common of these disorders, occurring in half to two thirds of cases (Rich et al., 1986, Henriksson et al., 1993, Conwell et al., 1996, Harwood et al., 2001). Every sixth death among individuals receiving treatment for depression by psychiatric services is by suicide (Wulsin et al., 1999). However, suicide risk varies with the nature of the depressive disorder and other factors (e.g. previous history). Just over a quarter of those who die by suicide with major depression are in contact with psychiatric services at the time of their death (National Confidential Inquiry into Suicide and Homicide by People with Mental Illness, 2006, National Confidential Inquiry into Suicide and Homicides by People with Mental Illness, 2012), indicating that primary care may also have a vital role to play in suicide prevention in this group. Approximately 50% of those who die by suicide have seen their general practitioner in the three months before death, 40% in the month beforehand, and 20% in the week before death (Barraclough et al., 1974, Pirkis and Burgess, 1998). Depression is a very common disorder in the general population (Joyce, 2012) and, therefore, detection of individuals at risk of suicide, while clearly extremely important, can be difficult. The identification of key risk factors for suicide in individuals with depression is therefore essential if clinicians are to identify those most at risk and intervene appropriately, as there is good evidence that monitoring and active treatment in high-risk patients may result in reduced suicide rates (Isometsa et al., 1994).

There is an extensive literature on risk factors for suicide (Hawton and van Heeringen, 2009), including in depression (Lönnqvist, 2000). But as far as we are aware there have been no systematic reviews which have assimilated the findings of studies specific to people with depression. We have conducted a systematic review of international literature on risk factors for suicide in people with depression.

Section snippets

Study eligibility

Studies were selected for inclusion if they met the following criteria:

  • i.

    The included patients had an ICD-10 diagnosis of depressive disorder (F32) or recurrent depressive disorder (F33), or a DSM-IV diagnosis of major depressive disorder. Samples using earlier versions of these diagnostic systems for unipolar depressive disorder were also included. The following diagnostic categories were included: unipolar depression, major depression disorder, depressive disorder NOS, melancholia, and mood

Results

The search strategy identified 3374 papers for potential inclusion. Of these, 155 were retrieved for a detailed evaluation. Thirty-two articles fulfilled the detailed eligibility criteria. Four publications had to be excluded as the authors were not able to provide the original data that we needed. Hence, 28 articles were included in this review, from a total of 19 studies. There were no unpublished studies. Of these, 9 were cohort studies and 9 were case-control studies, and one study combined

Discussion

Depression is strongly associated with suicide and non-fatal suicidal behaviour and ongoing assessment of suicide risk should be integral to the management of patients with this disorder. In this study we have focused on risk of suicide as this will be the principal concern of clinicians.

We have used a systematic approach to searching the world research literature on risk factors for suicide in people with depression, including studies in any language. Some authors reanalysed data for us,

Role of funding source

This study was supported by a grant from the Judi Meadows Memorial Fund and Maudsley Charity. The funder had no role in the study design; in the collection, analysis or interpretation of the data; in the writing of the report; and in the decision to submit the paper for publication. Keith Hawton is a National Institute for Health Research Senior Investigator.

Conflict of interest

The authors declare no conflict of interest.

Acknowledgements

The authors thank D. Brent, Y. Conwell, J. Fawcett, L. Mehlum, M. Silverman, G. Turecki, and M. Valenstein for checking the initial list of identified studies. The authors also thank L. Brådvik, W. Coryell, E. Høyer, M. Ilgen, C. Mattisson, B. Schneider, G. Turecki, R. Violette, A. Wang, and K. Zivin for supplying us with additional data from their studies.

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