There is considerable need for accurate suicide risk assessment for clinical, screening, and research purposes. This study applied the tripartite affect-behavior-cognition theory, the suicidal barometer model, classical test theory, and item response theory (IRT), to develop a brief self-report measure of suicide risk that is theoretically-grounded, reliable and valid. An initial survey (n = 359) employed an iterative process to an item pool, resulting in the six-item Suicidal Affect-Behavior-Cognition Scale (SABCS). Three additional studies tested the SABCS and a highly endorsed comparison measure. Studies included two online surveys (Ns = 1007, and 713), and one prospective clinical survey (n = 72; Time 2, n = 54). Factor analyses demonstrated SABCS construct validity through unidimensionality. Internal reliability was high (α = .86-.93, split-half = .90-.94)). The scale was predictive of future suicidal behaviors and suicidality (r = .68, .73, respectively), showed convergent validity, and the SABCS-4 demonstrated clinically relevant sensitivity to change. IRT analyses revealed the SABCS captured more information than the comparison measure, and better defined participants at low, moderate, and high risk. The SABCS is the first suicide risk measure to demonstrate no differential item functioning by sex, age, or ethnicity. In all comparisons, the SABCS showed incremental improvements over a highly endorsed scale through stronger predictive ability, reliability, and other properties. The SABCS is in the public domain, with this publication, and is suitable for clinical evaluations, public screening, and research.

Introduction

Suicide continues to be a leading cause of death, touching the lives of people from every corner of the globe, and ranks as the 16th leading cause of death [1]. Despite the seriousness and universality of this problem, instruments that evaluate and predict suicidality have not received the full attention they deserve. Demand is strong for empirically validated measures of personal risk for clinical and research efforts [2, 3]. However, many current instruments are inadequate for evaluation purposes [4]. Perhaps more than any other type of psychosocial assessment, suicide risk measures require focus on the minutiae of their psychometric properties and the validity of their outcomes. This study was aimed at producing incremental improvements in suicide risk evaluation by developing a brief self-report measure that incorporates theory and empirically evidenced suicidality attributes.

Suicide Risk Assessment Models It is imperative that the purpose of a test is clear and the instrument appropriate for the purpose [5, 6]. Suicide risk measures typically have two important goals, to assess both current suicidality and the potential for future suicidal behaviors. Currently, some clinicians choose not to use standardized suicide risk scales due to their overconfidence in clinical interviewing, and a perception that the instruments fail to capture essential aspects of suicidality [7]. However, an expert group concluded that clinicians are also unlikely to assess the suicidal person’s inner state, their subjective experience of being suicidal [8]. Risk assessment models can help guide and encourage professional evaluations. The tripartite model postulates that an attitude (e.g., toward suicide or death) is comprised of three correlated but distinct components: affect, behavior, and cognition [9]. The ABC model encompasses common suicidality factors, which might be useful for assessing suicide risk [10]. Kral and Sakinofsky [11] proposed a two-tier clinical assessment model that includes sociodemographic factors to understand the client’s general risk level, and subjective factors (thoughts, emotions, suicidal history) to identify individual risk, but has been inadequately tested. Incorporating demographic factors may, however, be counterproductive for standardized individual assessment [12]. Many suicide risk measures, such as the SAD PERSONS [13] and the Manchester Self Harm Rule (MSHR) [MSHR; 14], use dichotomous items on demographics and select risk and protective factors. However, these indexes have been criticized for inaccurate risk classifications, which can lead to a drain on psychiatric services [15, 16]. Jobes’ Suicide Status Form (SSF) [17] is a clinician-administered measure stemming from the theoretical works of Shneidman (psychological pain, agitation) [18], Beck (hopelessness) [19], and Baumeister (self-hate) [20]. It includes items on suicidal affect, behaviors, and cognition. The SSF is the most likely candidate for a gold standard in clinical evaluation. Unfortunately, its’ length and inclusion of qualitative responses make it inconvenient for some screening and research applications. Following on Shneidman’s [18] depiction of suicidality as a “storm in the mind,” and ABC theory, the suicidal barometer model (SBM) was recently introduced to guide risk evaluations. The SBM is based on theory and empirical evidence that suicidality is a volatile state, with strong implications for both current and future personal risk [11, 21, 22]. The SBM proposes that risk measures should capture the individual’s experience of that internal storm, through subjective behavioral intentions, life-death affect, and suicidal cognition.

Suicidal Affect, Behavior, and Cognition Affect is the most ambiguous factor of the tripartite model and the least common for suicidality assessment. Several terms have been used that might be regarded as death or suicide-related affect. They include the wish to live (WTL) and wish to die (WTD), which Kovacs and Beck referred to as a “motivational dimension” [23], emotions [21], and passive ideation [24]. Hopelessness is an affect with strong associations to suicidality. The Beck Hopelessness Scale (BHS) has proven useful in research and risk assessment, and might be a unique suicidal attribute [19, 25]. There is, however, some contradictory evidence on relationships between affect and suicidality. A study of patients presenting with suicidal symptoms found inconsistent associations between affect and suicide attempt status [26], while a large longitudinal study determined the combination of lifetime cognition and death-related affect were the best predictors of suicide death [24]. WTL and WTD items have proven useful in assessing suicidality, and are included in Beck’s Scale of Suicidal Ideation (SSI) [27], and the SSF [28]. Overall, there is strong evidence that suicidal affects can be valid indicators of current and future risk. A considerable body of empirical evidence demonstrates suicidal behaviors, such as plans and attempts, can be predictive of suicide [29–31]. Of importance to risk assessment, research has shown that including the individual’s intent to die improves the validity of past suicidal behaviors as indicators of current and future risk [32, 33]. Many instruments, such as the Suicidal Behaviors Questionnaire-Revised (SBQ-R) [34] and the Suicide Intent Scale (SIS) [35], include items on communication of suicidality. However, Kovacs et al. [36] concluded, from an examination of US suicide attempters, that prior verbalization of suicidality had little relationship with WTD during the attempt, and may be a manifestation of personal style. More recently, a large study of French university students found higher risk suicide attempts included less communication of suicidality [37], while a psychological autopsy study of 200 Chinese suicide victims revealed about 60% had not communicated their suicidality, in any way, prior to death [38]. Non-suicidal self-harm (NSSH) is also included in some suicide risk measures, such as the Self-Injurious Thoughts and Behaviors Interview [39]. However, recent research found that including NSSH did not provide additional predictive ability to a model including suicidal cognition and behaviors [29]. Overall, there is considerable evidence that past suicidal plans and attempts should be considered for evaluation of current and future risk, but other behaviors, such as NSSH and communications, may not be valid factors for many individuals. Suicidal cognition, or ideation, is considered to be a defining attribute of suicidality [8, 40, 41]. Numerous studies have provided empirical evidence demonstrating the importance of suicidal cognition for current and future suicide risk [24, 29, 42]. Other than select instruments, such as the MSHR and SAD PERSONS, most suicide risk measures include at least one suicidal cognition item. Scales require relevant definitions of the construct to enable effective assessment [5, 6]. Many definitions of suicidality are strictly behavioral. The suicidal mind, the extremely distressing experience of the suicidal individual, is often absent. For example, one expert group defined suicidality as “completed suicide, suicide attempt, or preparatory acts toward imminent suicidal behavior” [43]. Some have even argued that the term suicidality be abandoned, with focus on specific suicidal behaviors [44]. Others propose better representation of the lived experience of being suicidal [7, 8]. For example, Shneidman described suicide as an “extreme (unbearable) psychological pain coupled with the idea that death (cessation) can provide a solution to the problem of seemingly unacceptable mental distress” [18]. For this study, we define suicidality as current suicide-related distress (which may include affective, behavioral, and cognitive attributes), with potential for future suicidal distress and behaviors.

Best Practice Scale Properties There are numerous factors to consider when developing or testing a measure. Unfortunately, those minutiae, forming the structure of the instrument, are often ignored in suicide risk assessment. Here, we summarize relevant findings and recommendations of psychometricians and scale development experts. Single-item measures of a construct, including suicidality as assessed in the Beck Depression Inventory (BDI II) [45] and the Patient Health Questionnaire (PHQ-9) [46], should be avoided as there are only rare situations when single items perform as well as validated multiple-item measures [5, 47]. Dichotomizing items (e.g., yes/no) or outcomes (e.g., suicidal/nonsuicidal), reduces validity by constraining the amount of information that can be captured on the latent trait, and should also be avoided whenever possible [48–50]. Some psychometricians have determined the ideal number of item response choices to be 4–7 [51, 52]. Fortunately, item response theory (IRT) analyses can help verify response format validity [48, 53]. Psychometric study has also shown that verbally labeled responses (e.g., poor, fair, good) differed by 0.7 to 1.3 points, rather than the equidistant 1.0 used for item scoring [54]. An advantage of verbally labeling only anchor points is obtaining interval level data, through equidistant response categories. Another important consideration is item weighting. IRT analyses can determine whether items make equal or disproportionate contributions to scale totals [48, 53]. Differential item functioning (DIF), or item bias, refers to a situation when respondents with the same trait level, but belonging to different groups, show dissimilar probability distributions on responses to a particular item [55]. IRT analyses have found DIF for white and Asian Americans on depressive symptoms [56], and for age groups on the BDI [57]. Similarly, classical test theory (CTT) analyses found lower internal reliability for Asian American university students, compared with white students, on the Positive and Negative Suicide Ideation inventory [58]. Those findings indicate that the measures do not function the same for some groups. DIF checks have yet to be applied to suicide risk assessment, although they are important procedures for test development and checking inter-group validity [59]. For scale development, representativeness on the target constructs does not require random sampling from target populations, it requires samples where relationships among items, or constructs, are the same as in target populations [5]. A recent study found a large university community sample reported lower ranges of high-risk mental health symptoms and substance use, and lower scale reliability, compared with an online community sample [60]. Another possible obstacle to response validity is social desirability bias [61, 62]. However, that can be significantly reduced, and self-disclosure of personal information increased, through anonymous assessment methods [62–64]. Online surveys may be particularly useful for examining suicidal individuals, as they have been shown to be more active online than nonsuicidal people [65, 66]. Those findings point to advantages of anonymous surveys and a possible weakness of university samples when developing measures of stigmatized constructs, such as suicidality. Given the empirical evidence for these fundamental scale development practices, the burden of proof is on test developers and administrators to justify variations, such as including dichotomous items or outcomes, or developing scales with only university students.

Current Measures of Suicidality/Suicide Risk While a full review of the numerous suicide risk measures is beyond the scope of this study, there are popular and recommended instruments that deserve consideration. Test administrators are likely to refer to expert recommendations to choose the best available measure for their purposes. However, expert opinions can be based on a variety of standards. In Range and Knott’s [21] earlier review of 20 suicide risk instruments, scales were judged to assess the theoretically important factors: emotion, behavior, and cognition. The authors determined that only 30% of those scales assessed an emotional component of suicide risk, only 25% at least two factors, while no instrument was judged to assess all three attributes. Based on reported reliability, validity, and theoretical grounding, they recommended the SSI, Linehan’s Reasons for Living Inventory, and the SBQ-R. The American Psychiatric Association [67] did not recommend any specific tool, but highlighted the SSI and SBQ-R as valuable in assisting clinical judgment. An expert panel in New Zealand recommended only the BHS, stating it “has the best generic application for screening for suicide risk amongst adults, adolescents, inpatients, outpatients and people seeking assistance from emergency departments” [68]. However, earlier research determined the SSI-W to be more effective than the BHS for assessing suicide risk [69]. The British Medical Journal, as part of their best practices initiative, recommended the Tool for Assessment of Suicide Risk (TASR), stating that it “helps to ensure that the most important issues pertaining to suicide risk are considered” [70]. The TASR [71] consists of dichotomous items on affect, behaviors, and cognition, as well as demographic factors (e.g., age, sex), medical illness, and reasons for living. The scale developers provided no psychometric properties of the instrument, nor any indication of its validity in assessing suicide risk. The SBQ-R and C-SSRS were two of four measures endorsed by the US Substance Abuse and Mental Health Services Administration’s Center for Integrated Health Solutions [72]. The initial study of the C-SSRS reported high internal reliability for a small sample (α = .95, N = 124), but low reliability with a larger sample (α = .73, N = 549) for one of four subscales, while others were not evaluated [73]. The C-SSRS consists of clinician-administered prompts with mostly dichotomous scoring options [74]. It includes cognition, behaviors, and one dichotomous item on affect. An electronic version (eC-SSRS) consists of ‘electronic’ clinician-administered dichotomous items, and demonstrated some predictive ability, but rather low sensitivity and specificity rates [75]. It is notable that few measures assess all three ABC attributes. The SSI includes items on cognition and affect, but behaviors are limited to current suicide planning and communications. The SIS includes items on suicidal affect and behaviors (regarding a recent attempt), but the one cognition item assesses impulsiveness of an attempt. The Adult Suicide Ideation Questionnaire [76] includes items on cognition and affect, but the behavior items are limited to suicidal communications. Nearly all of these instruments require fees for use. Currently, there are no known self-report public domain measures that include all ABC attributes.