Worry and pathological worry in patients with psoriasis: Cross sectional and longitudinal analyses of the Penn State Worry Questionnaire (PSWQ) in four samples of patients

The purpose of the present study was to examine the psychometric properties of the Penn state Worry Questionnaire (PSWQ) in patients with psoriasis. A series of cross-sectional and longitudinal studies were undertaken to assess the reliability, stability and validity of the measure. Patients with psoriasis from four samples (consecutive attendees, anxious patients, depressed patients, and 6-month follow-up of consecutive attendees) completed the PSWQ and measures assessing related constructs of anxiety and depression (HADS) and coping (COPE). The clinical severity of patient's psoriasis was also assessed by dermatologists using the Psoriasis Area and Severity Index (PASI). Exploratory factor analysis was undertaken and receiver operator characteristic (ROC) analyses were used to examine the clinical utility of the PSWQ cut-off score for normal and pathological worry. Exploratory factor analysis suggested that the PSWQ is essentially unidimensional in patients with psoriasis. Intraclass correlation demonstrated that, over a 6-month period, the reproducibility of the PSWQ total scale was good in patients with anxiety and moderate in patients with depression. ROC analysis suggested that the optimum cutoff differentiating pathological worry was > 60, which is commensurate with findings in adult mental health more generally. The PSWQ cutoff for pathological worry showed a lower specificity for depression than anxiety. The PSWQ is an appropriate measure of pathological worry in patients with psoriasis. The cutoff on the scale for pathological worry demonstrates appropriate conceptual overlap with subordinate distress categories of anxiety and depression.