Do Suicidal Desire and Facets of Capability for Suicide Predict Future Suicidal Behavior? A Longitudinal Test of the Desire-Capability Hypothesis

Capability-based models propose that people die by suicide because they want to, and they can. Despite the intuitive appeal of this hypothesis, longitudinal evidence testing its predictive validity has been limited. This study tested the predictive validity of the desire-capability hypothesis. A total of 1,020 selfinjuring and/or suicidal adults were recruited worldwide online from suicide, self-injury, and mental health web forums. After baseline assessment, participants completed follow-up assessments at 3, 14, and 28 days after baseline. Participant retention was high (>90%) across all follow-up assessments. Analyses examined the effect of the statistical interaction between suicidal desire and indices of capability for suicide on future nonfatal suicide attempts. Main analyses focused on the fearlessness about death facet of capability for suicide; exploratory analyses examined preparations for suicide. Logistic regression was used to predict suicide attempt status at follow-up; zero-inflated negative binomial models were implemented to predict the frequency of nonfatal suicide attempts at follow-up. Results were consistent across models, finding very little evidence of the desire-capability interaction as a significant predictor of suicide attempt status or frequency at follow-up. We close with a discussion of the limitations of this study as well as the implications of our findings for future suicide science.