Objectives: Traits related to a hyper-reactive arousal system (arousability) and weakened sleep system (sleep reactivity) are considered predisposing factors for insomnia of potential clinical utility. However, research examining the psychometric properties (ie, reliability and validity) of the Arousal Predisposition Scale (APS) and its clinical utility (ie, cut-off scores) among population-based and clinical samples is very limited. Methods: A total of 500 adults (41.8% female, 39.1 ± 15.9 years) from the general population in Spain and 217 adults (64.5% female, 46.0 ± 16.1 years) from a clinical sample in the United States completed the APS, as well as measures of sleep reactivity, insomnia severity, anxiety, depression, and stress. Structural equation modeling was used to conduct confirmatory factor analysis (CFA) of the APS. Correlation and receiver operating characteristic (ROC) analyses were used to determine convergent and predictive validity of the APS and its factors. Results: The CFAs supported two dimensions of emotional reactivity (APS-ER, 9 items) and trait anxiety (APS-TA, 3 items) in both independent samples. APS-ER was associated with sleep reactivity and performed better than APS-TA when predicting clinically significant sleep reactivity and similarly when predicting clinically significant insomnia severity. Conclusions: Our findings support the specificity of emotional reactivity and sleep reactivity as trait predispositions to insomnia, while trait anxiety is a predisposing factor for the comorbidity of insomnia with state anxiety rather than a specific diathesis for insomnia. These data provide further support for the diathesis-stress model of insomnia and, as a transdiagnostic process, its potential etiological link with psychopathology.
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