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