Affective and sensory dimensions of pruritus severity: associations with psychological symptoms and quality of life in psoriasis patients.

The subjective dimensions of pruritus and their associations with psychological symptoms and quality of life were explored in a sample of 40 psoriasis patients. The patients completed a scale with descriptors from the Structured Itch Questionnaire together with measures of depression, distress, sleep quality and pruritus-related quality of life. Psoriasis severity was assessed with the Psoriasis Area and Severity Index. Factor analysis of descriptors confirmed both an affective and a sensory pruritus severity dimension. Multivariate statistics, controlling for age, gender, disease duration and severity, showed affective, but not sensory, pruritus severity to be a significant predictor of depressive symptoms, global distress, impairment of sleep, and pruritus-related quality of life. Mediation analyses indicated that impaired sleep quality partly mediated the association between pruritus severity and psychological symptoms. The results confirm that pruritus is multidimensional and indicate that the affective dimension may be the most important predictor of pruritus-related psychological morbidity, and that the association may be mediated by its negative impact on sleep quality.