A prospective Japanese population-based cohort study in 2,224 participants investigated the relationship between frequency of pruritic symptoms (over 1 month) and psychological stress. Pruritic symptoms were reported by patients in health diaries and psychological stress was measured with the Japanese version of the Perceived Stress Scale (PSS). Patients with pruritic symptoms (n = 70) had significantly more psychological stress than those without (n = 2,154; P = 0.01). A linear trend was seen between increasing psychological stress and increased frequency of pruritic symptomatology (p for trend = 0.004) (Yamamoto, Y. et al. Arch Dermatol 2009, 145(12): 1384).