Psychometric properties of the Suicidal Ideation Attributes Scale (SIDAS) in a longitudinal sample of people experiencing non-affective psychosis

BACKGROUND: Suicidal ideation is a key precursor for suicide attempts and suicide deaths. Performing routine screening of suicide precursors can help identify people who are at high risk of death by suicide. This is, arguably, an important suicide prevention effort. The aim of this study was to assess the validity, reliability, and factor structure of the Suicidal Ideation Attributes Scale (SIDAS) in a three-month longitudinal study with people with a diagnosis of schizophrenia or non-affective psychosis and experiences of suicidal ideation and/or behaviours. It was predicted that the SIDAS would have high internal consistency, test-retest reliability, convergent, discriminant and construct validity. METHODS: Ninety-nine participants experiencing psychosis completed the SIDAS at baseline and 89 participants completed it 3 months later. Additionally, participants completed a demographic questionnaire, the Beck Scale for Suicide Ideation, the Beck Hopelessness Scale, and the Defeat and Entrapment Scales. The internal consistency, test-retest reliability, convergent validity, and discriminant validity of the SIDAS were investigated in comparison to other constructs. Factor analysis was performed to examine the factor structure of the scale. RESULTS: Principal component analysis yielded a theoretically coherent one-dimensional factor structure of SIDAS, suggesting good construct validity (PCA = .71). The SIDAS had high internal consistency (α = .89) and good test-retest reliability (α = .73). It was highly correlated with other self-report measures, including the Beck Scale for Suicide Ideation, Beck Hopelessness Scale, Defeat and Entrapment scales, indicating excellent construct validity. CONCLUSION: The SIDAS is a valid and reliable self-report instrument for assessing the severity of suicidal ideation in a population of people with a diagnosis of schizophrenia or non-affective psychosis. Further research should test the psychometric properties of the scale in individuals experiencing different mental health problems in cross-cultural settings, in order to establish its broader validity, reliability, and clinical utility.