Use of the acquired capability for suicide scale (ACSS) among United States military and Veteran samples: A systematic review

Background: Military personnel and Veterans are at increased risk for suicide. Theoretical and conceptual arguments have suggested that elevated levels of acquired capability (AC) could be an explanatory factor accounting for this increased risk. However, empirical research utilizing the Acquired Capability for Suicide Scale (ACSS) in military populations has yielded mixed findings. Methods: To better ascertain what factors are associated with AC, and whether methodological limitations may be contributing to mixed findings, a systematic review was conducted. Results: A total of 31 articles utilized the ACSS to examine factors associated with AC, including combat history, in United States (U.S.) military personnel and Veterans. Nearly all studies (96.8%) were rated high risk of bias. Use of the ACSS varied, with seven different iterations utilized. Nearly all studies examined correlations between the ACSS and sample characteristics, mental health and clinical factors, Interpersonal Theory of Suicide constructs, and/or suicide-specific variables. Results of higher-level analyses, dominated by cross-sectional designs, often contradicted correlational findings, with inconsistent findings across studies. Limitations: Included studies were non-representative of all U.S. military and Veteran populations and may only generalize to these populations. Conclusions: Due to the high risk of bias, inconsistent use of the ACSS, lack of sample heterogeneity, and variability in factors examined, interpretation of current ACSS empirical data is cautioned. Suggestions for future research, contextualized by these limitations, are discussed.