A population-based longitudinal study of suicide risk in male schizophrenia patients: Proximity to hospital discharge and the moderating effect of premorbid IQ

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Abstract

Suicide is a major cause of death in schizophrenia. Identifying factors which increase the risk of suicide among schizophrenia patients might help focus prevention efforts. This study examined risk of suicide in male schizophrenia patients using population-based data, examining the timing of suicide in relation to the last hospital discharge, and the effect of premorbid IQ on risk of suicide.

Data on 930,000 male adolescents from the Israeli military draft board were linked with data from the Israeli Psychiatric Hospitalization Case Registry and vital statistics from the Israeli Ministry of Health. The relationship between premorbid IQ and risk for suicide was examined among 2881 males hospitalized with schizophrenia and compared to a control group of 566,726 males from the same cohort, who were not hospitalized for a psychiatric disorder, using survival analysis methods.

Over a mean follow-up period of 9.9 years (SD = 5.8, range: 0–22 years), 77/3806 males with schizophrenia died by suicide (a suicide rate of 204.4 per 100,000 person-years). Approximately 48% of the suicides occurred within a year of discharge from the last hospital admission for schizophrenia. Risk of suicide was higher in male schizophrenia patients with high premorbid IQ (HR = 4.45, 95% CI = 1.37–14.43) compared to those with normal premorbid IQ.

These data indicate that male schizophrenia patients with high premorbid IQ are at particularly high risk of suicide, and the time of peak risk is during the first year after the last hospitalization discharge.

Introduction

Recent meta-analytic estimates on risk for suicide in schizophrenia have placed the lifetime risk of suicide at about 5% (Hor and Taylor, 2010, Palmer et al., 2005). A number of studies have found that risk of suicide is elevated among psychiatric patients during the initial period after discharge from hospital (Hjorthoj et al., 2014, Qin and Nordentoft, 2005). Several relatively small studies (De Hert et al., 2001), some retrospective (Fenton, 2000, Westermeyer et al., 1991), and two large population-based studies (Andersson et al., 2008, Webb et al., 2011), have shown that risk for suicide in schizophrenia is increased in patients with higher IQs, whereas among the general population, high IQ is associated with reduced risk of suicide (Andersson et al., 2008). Similarly, a national cohort study on psychotic patients indicated that patients who had completed their academic obligations (as opposed to those who had not completed their academic obligations) from compulsory school were at increased risk of suicide (Björkenstam et al., 2014). A systematic review also indicated that a higher level of education was associated with increased risk of suicide among schizophrenia patients (Hor and Taylor, 2010).

Identifying predictors of suicide in schizophrenia is necessary in order to focus preventive measures to those who are at highest risk, a task important from both clinical and public health perspectives. Using a population-based, historical prospective design, this study identified 930 000 male adolescents assessed by the Israeli military at age 17, and used databases to follow them up for later psychiatric hospitalization and suicide. Based on previous reports, we investigated whether (1) the period of time immediately following hospital discharge (the patients' last hospitalization discharge) is a period of particular vulnerability for suicide, and (2) schizophrenia patients with higher premorbid IQ are at increased risk for suicide.

Section snippets

Materials and methods

Data from three separate, comprehensive, nation-wide databases were linked: the pre-induction assessment of adolescents by the Military Draft Board, hospitalization and diagnosis data from the Psychiatric Hospitalization Case Registry, and death registered by the Ministry of Health. In order to protect patients' anonymity, patient identifiers were encrypted before the datasets were merged.

Results

Male schizophrenia patients were at particularly high risk for suicide in the period following the last hospitalization (Table 1): out of 77 definite cases of completed suicides, 32.5% of all definite suicides occurred within the first six months following discharge from the last hospital admission and 48.1% occurred within a year of discharge from the last hospitalization. The mean age of suicide in male schizophrenia patients was 27.0 years, similar to the mean age of suicide in the control

Discussion

This large, longitudinal, population-based study has two main findings: that suicide in male schizophrenia patients is associated with proximity to the last hospitalization, and that male schizophrenia patients with high premorbid IQ have increased risk for suicide compared to those with normal premorbid IQ. We found a significant interaction between high (vs. normal) premorbid IQ and study group (male schizophrenia patients vs. male controls) for risk of suicide

Role of funding source

There were no funding sources for this study.

Contributors

Prof. Mark Weiser takes responsibility for the integrity of the work as a whole, from inception to the published article. Prof. Weiser conceived and designed the study, participated in analysis and interpretation of the data, critically revised it for important intellectual content and approved the final manuscript. Ori Kapra and Shira Goldberg analyzed and interpreted the data, drafted the manuscript, and gave approval of the final manuscript. Daphna Fenchel analyzed the data and was

Conflict of interest

The authors have no conflicts of interest including relevant financial interests, activities, relationships, and affiliations.

Acknowledgment

No acknowledgments.

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