Psychological factors in prurigo nodularis in comparison with psoriasis vulgaris: results of a case-control study

BACKGROUND: It has been suggested that psychological factors such as repressing anger and altruistic interpersonal behaviour may play a role in the aetiology of chronic itching in prurigo nodularis (PN). Whether these issues are specific for PN or are also common in other chronic skin diseases, e.g. psoriasis, has not been investigated until now. OBJECTIVES: To investigate psychosomatic problem areas and psychiatric comorbidity in patients with PN in comparison with patients with psoriasis. METHODS: Ninety-four patients with PN and 91 patients with psoriasis were administered the Hospital Anxiety and Depression Scale, Toronto Alexithymia Scale, State-Trait Anger Expression Inventory, Inventory of Interpersonal Problems, Screening for Somatoform Disorders and the Whiteley Index for hypochondriasis. RESULTS: After Bonferroni post hoc adjustment, the metrical scales demonstrated no significant differences between patients with PN and those with psoriasis. There was only a tendency to less 'anger-out' and to less autocratic/dominant and more insecure/submissive behaviour in the patients with PN. Patients with PN were, in general, comparable with those with psoriasis with regard to alexithymia, somatization symptoms, hypochondriasis, anxiety and depression, with 18% cases of anxiety and 22% cases of depression. CONCLUSIONS: The hypotheses formulated in the literature on the specific aetiology of PN could not be proven for the majority of patients with PN in our study. Concerning their psychopathology, patients with PN were comparable with those with psoriasis. Therefore the clinical management of PN should include psychosomatic assessment.