Preserved cognitive function is associated with suicidal ideation and single suicide attempts in schizophrenia
Introduction
Suicide is the leading cause of premature death in schizophrenia (Palmer et al., 2005). Between 4% and 13% of patients with a diagnosis of schizophrenia commit suicide, and up to 60% of patients make at least one suicide attempt (Caldwell and Gottesman, 1990, Inskip et al., 1998). A variety of factors are associated with increased risk. These include age, severity of depressive symptoms, and impulsive agressive traits (Barak et al., 2008, McGirr et al., 2008). In non-psychotic patients, poor cognitive ability has been associated with an increased risk of self-harm and suicide (Jiang et al., 1999, Gunnell et al., 2005). In schizophrenia, which is associated with both general and specific cognitive deficits, the relationship between suicidality and cognition is unclear.
De Hert et al. (2001), in a study of 63 cases, found that high pre-morbid IQ was one of four predictors (along with younger age, female gender, and co-morbid physical illness) of increased suicide attempts. Kim et al (2003), in a study of 151 patients who completed an extensive neurocognitive battery, found that attempted suicide was associated with better performance on indices of executive control (indexing pre-frontal lobe function) but not IQ. A previous study by our group (Nangle et al., 2006) similarly found an association between increased suicide attempts and better cognitive function, particularly for measures of attentional control. This association between suicidality and better cognition has been explained in terms of both goal-directed behavior (Nangle et al., 2006) and better insight, which itself is associated with better cognitive function (Crumlish et al., 2005, Donohoe et al., 2009). However, in another comparison between non-attempters and multiple suicide attempters, no difference in cognitive performance was observed (Potkin et al., 2003). Several questions remain about the relationship between suicidality and neuropsychological performance. First, it is unclear whether the influence of cognitive ability on suicidality in patients who express suicidal ideation or make a single suicide attempt is comparable to the influence on those who make multiple suicide attempts. It may be that single attempters show greater cognitive ability and insight, whereas multiple attempters are expressing coping difficulties that are either unrelated to cognitive ability or reflective of a poorer cognitive capacity. Such a distinction has not been empirically tested to our knowledge and may help to explain the inconsistencies in the literature to date. Second, it is unclear whether the relationship between suicidality and cognitive performance is specific to individual cognitive domains (e.g. executive functioning) or to cognition more generally.
We investigated the relationship between neurocognitive performance and suicidality using patient histories which documented both the nature and extent of their suicidality. We hypothesized, based on our previous study, that a history of suicidality would be associated with relatively preserved cognitive function. We also investigated the exploratory hypothesis that cognitive performance would differ according to the nature and extent of suicidality (i.e. between those with suicidal ideation, those making single suicide attempts, and those making multiple suicide attempts).
Section snippets
Sample selection
The sample consisted of 310 clinically stable patients with a diagnosis of schizophrenia or schizoaffective disorder. Inclusion criteria necessitated that participants be aged 18–65 years with no history of co-morbid psychiatric disorder, substance abuse in the preceding 6 months, prior head injury with loss of consciousness, or seizures. Diagnosis was confirmed by trained psychiatrists using the Structured Clinical Interview for DSM-IV Axis 1 Diagnoses (SCID). Symptom severity was assessed using
Suicidality and clinical characteristics
One hundred and seventy two patients (54.4%) were classified as non-attempters with no ideation, sixty three patients (19.9%) as having a history of ideation without having made a suicide attempt, forty eight patients (15.2%) as having made a single attempt, and twenty seven patients (8.5%) as having made multiple attempts. No differences in age, gender, age of onset, diagnosis (schizophrenia versus schizoaffective disorder), or medication dosage (expressed in chlorpromazine equivalents) were
Discussion
The aim of this study was to examine the relationship between neuropsychological function and suicidality in patients with schizophrenia or schizoaffective disorder. Specifically, we investigated whether the nature and extent of suicidal ideation and behavior were influenced by neuropsychological function. In summary, there were three findings. First, patients with a history of suicidal ideation and those with a history of a single suicide attempt were comparable in their neuropsychological
Conclusion
The present study aimed to clarify the relationship between global and specific measures of cognitive function and suicidality in schizophrenia. Our results demonstrated significant differences in neurocognitive function between those that had expressed suicidal ideation and/or made a single suicide attempt and those that had neither contemplated nor attempted suicide. This was consistent with previous studies which observed an association with preserved cognitive function and suicidality in
Role of funding source
No funding body had any part in how this study was conducted or in how this manuscript was written.
Contributors
Donohoe, Delaney and McGrath designed the study. Delaney and McGrath carried out the statistical analysis. Cummins, Morris, Corvin and Donohoe, and Gill contributed to collection of the data. All authors contributed to the writing and editing of the final manuscript and have approved its contents.
Conflict of interest
All authors disclose that they have no conflict of interest in relation to the publication of this manuscript and its contents.
Acknowledgements
This work was supported by a student grant from the Irish Health Rerearch Board to JMcG. Recruitment of the Irish sample was supported by the Wellcome Trust and Science Foundation Ireland (SFI). Dr. Donohoe's work is supported by an HRB research project grant.
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Both authors contributed equally to this work.