Is suicidal behaviour a stronger predictor of later suicide than suicidal ideation? A systematic review and meta-analysis

Objective: Suicidal ideation and suicidal behaviour are both regarded as important risk factors for suicide, but it is usually believed that suicidal ideation is less strongly linked to suicide than suicidal behaviours. In this study, we assessed and compared the strengths of the associations that suicidal ideation and suicidal behaviour have with later suicide using meta-analysis of primary studies reporting both these independent variables and the dependent variable of suicide. Methods: A total of 51 English language publications describing cohort or controlled studies that reported on both the association between suicidal ideation and suicide and the association between suicidal behaviours and suicide were located using searches for titles in PubMed containing variants of the word suicide (suicid*). Suicides were considered to include reported suicides and open verdicts from mortality registers. The strengths of the two associations were examined in separate random effects meta-analyses and were then compared using mixed effects meta-regression. Subgroups were examined according to study characteristics including the definitions of suicidal ideation or behaviour used, setting (psychiatric or non-psychiatric), diagnostic mix of the study population, study design (cohort or control) and study quality. Results: Suicidal ideation (odds ratio = 3.11, 95% confidence interval = 2.51, 3.86) and suicidal behaviours (odds ratio = 4.09, 95% confidence interval = 3.05, 5.49) were both significantly associated with suicide but there was no significant difference in the strengths of association (p = 0.14). Nor were there significant differences in the strengths of the two associations in multiple subgroup analyses. Conclusion: Suicidal ideation and suicidal behaviour are both moderately associated with suicide. Existing data cannot conclusively demonstrate that suicidal behaviours are more strongly associated with suicide than suicidal ideation. Clinicians should not strongly prioritise suicidal behaviour over suicidal ideation when considering suicide risk.