Psychometric Properties of the European Portuguese Adaptation of the Insomnia Catastrophizing Scale (ICS)

The current study developed the first translation and adaptation of the ICS (Insomnia Catastrophizing Scale) into European Portuguese, and studied its psychometric properties. The ICS evaluates the catastrophic thoughts related with insomnia symptoms during sleeping time (ICS-N) and during daytime functioning (ICS-D). We recruited a community-based sample of 802 Portuguese participants, aged ≥ 18 years, where approximately 80% of the sample were women. The results showed that the scale has good internal consistency values for both the ICS-N (α = 0.93) and ICS-D (α = 0.95) subscales. Factor analyses suggested the presence of a single factor in both measured scales. Posteriorly, the sample was divided into two groups labeled “Insomnia” (n = 170) and “no Insomnia” (n = 632). For all the items of each one of the subscales, it was observed that “insomnia” individuals presented higher scores than “no insomnia” group. Finally, the Receiver Operating Characteristics curves were computed for both subscales, extracting the cut-off points based on optimal sensitivity (ICS-N = 75.9%; ICS-D = 65.9%) and specificity ICS-N = 75.6%; ICS-D = 77.8%) values. Overall, these findings show similarities with the other published studies with ICS. The ICS seems to be a good psychological assessment measure used in clinical and research settings.