Summary

Introduction

Methods

Role of the funding source

Results

Discussion

Data sharing

Acknowledgements

Contributors

Supplementary materials

References

Summary

Background

     The aim of the study was to crystallize the nature of relationships between impulsivity, aggression, and suicidality. We reviewed studies of adults with published, psychometric measures of impulsivity and aggression, and measures of suicidality.

Methods

     Our primary data source was Web of Science (from inception to 31st December 2021). Quality of articles was assessed using a Joanna Briggs Appraisal Tool and publication bias using Trim and Fill. We synthesised results using random effects meta-analyses and explored moderation by measure of impulsivity, aggression, and suicidality, and population.

Findings

     ۷۷ studies were included in our analysis. We found weak positive relationships between impulsivity (r = 0·۱۹ [۹۵% CI: 0·۱۵–۰·۲۲]), aggression (0·۲۳ ([۰·۱۷, ۰·۲۹]), and impulsive aggression (0·۱۶ [۰·۱, ۰·۲۲]) with suicidality. Heterogeneity was significant and only partially explained by moderators. Limitations included the lack of studies which assess impulsivity or aggression proximal to suicidality.

Interpretation

     Given small effect sizes and significant heterogeneity, the study suggests that additional studies are needed in the field to analyze the relation between impulsivity and aggression with suicidality.

Introduction

     Despite a large body of research identifying population-level risk factors we remain poor at identifying individuals at risk of suicide.1,  ۲,  ۳,  ۴,  ۵,  ۶,  ۷,  ۸,  ۹ Counting risk factors alone performs no better than chance,6 actuarial risk assessment tools are wrong 95% of the time,7,8 and clinicians report low confidence in risk assessment.9 This may reflect limited validity of the theoretical models which underpin risk assessment. Here we focus on two key constructs widely believed to be related to suicidality and included in multiple theoretical models and risk assessment tools, but whose relationships are characterized by inconsistency in the empirical literature: impulsivity and aggression.

     Impulsivity is a broad construct that has multiple operationalizations.10,11 Definitions include risk-taking, sensation-seeking, behavioral disinhibition, preference for small immediate rewards over large distal rewards, deficits in planning, and urgency.10 It is included in three leading theoretical models of suicide.12 In Beck et al.’s Cognitive Model,13,14 impulsivity is a dispositional trait which increases suicidality. In Baumeister’s Escape Theory,15 suicidality increases when individuals can no longer resist impulsive urges to remove themselves from distress via increased behavioral disinhibition. In the Integrated Motivational Volitional Model,16,17 impulsivity acts as a volitional moderator between suicidal ideation and action.

Results

     The search returned 10,348 items. FM screened titles and removed duplicates and studies outside the area of interest, reviews or theoretical reports, case studies, or those that stated inclusion of participants under 16 (n = 9622). FM screened the abstracts of the remaining 726 articles in accordance with eligibility criteria. Forward and backward searching of reference lists of all eligible studies identified one additional item. Full articles were screened against the Joanna Briggs Checklist for Analytical Cross-Sectional Studies.43 As our eligibility criteria closely matched the Checklist criteria, there was no instance where a study met our inclusion criteria but scored below 100% on relevant items (i.e. 8 out of 8 if identification and management of confounding variables was appropriate, and 6 out of 6 if not) on the Checklist. Given the lack of variance in scores, we did not include this measure of quality as a covariate in analyses. HM independently evaluated a sub-set of 10% of the articles, yielding concordance of 98% (i.e. two discrepancies which were discussed and agreed). Our decision to check concordance in a subset of the articles was based on the large number of articles to be screened, and the high rate of concordance across the 10% sample, from which we concluded further testing would be unlikely to improve the validity of the sample. Seventy-seven studies from 75 samples were included in the review. See Figure 1 for a summary of the selection process.