Capability for suicide interacts with states of heightened arousal to predict death by suicide beyond the effects of depression and hopelessness

Background
States of heightened arousal (e.g., agitation, sleep disturbance) have been repeatedly linked to suicidal thoughts and behaviors, including attempts and death. Studies have further indicated that these states may be particularly pernicious among individuals who evidence high suicidal capability. The objective of this study was to examine the interactive effects of heightened arousal and the capability for suicide in the prospective prediction of death by suicide. We examine this relation beyond the effects of robust predictors of suicide, namely depression and hopelessness.
Methods
Participants were drawn from a larger study of undergraduates who completed baseline assessments during their freshman year and were then followed to time of death. The sample in this study only included individuals who had died by suicide (n=96) or other causes (n=542). Proxy measures to assess predictor variables were constructed using items from the MMPI, which was administered at baseline. An independent sample of clinical outpatients (n=was used to evaluate the construct validity of the proxy measures).
Results
Results were in line with expectation: heightened arousal interacted with capability for suicide to prospectively predict death by suicide, such that, as severity of heightened arousal symptoms increased, the likelihood of death by suicide increased among individuals high but not low on capability for suicide.
Limitations
Limitations include the use of proxy measures, the extended length of follow-up, and the homogeneity of the sample (i.e., primarily White males).
Conclusion
These findings add to an emerging literature that supports the moderating influence of capability for suicide on the relationship between states of heightened arousal on the likelihood of death by suicide.