Reduction of Plasma Levels of Neurotrophins by Laughter in Patients with Atopic Dermatitis

Abstract

Patients with atopic dermatitis (AD) are afflicted with a distressing, chronically relapsing, extremely pruritic eczema. The pruritus often produces stress in these patients. However, many "triggers" (i.e., sweating, xerosis, some allergens, etc.) are known to produce their itch. "Stress" is well-recognized as another "trigger" of their pruritus. In contrast, laughter reduces allergic responses. The effect of laughter on plasma neurotrophic levels caused by viewing humorous videos was studied in AD patients. The study was conducted using a cross-over design. Twenty-four patients with moderate AD (SCORAD index mean age 14 years, range 13–15 years) and 24 normal subjects (mean age 14 years, range 13–15 years) randomly viewed an 87-minute-long nonemotional weather information video and an 87-minute-long humorous video movie (Modern Times, featuring Charlie Chaplin). Just before and immediately after viewing each video, stress levels were measured using a one-item overall stress-rating scale. Simultaneously, blood was drawn and plasma levels of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neutrophin-4 (NT-4) were measured. Stress levels and plasma levels of NGF, BDNF, NT-3, and NT-4 were significantly elevated in patients with AD. Viewing the humorous video reduced the one-item rating scale and plasma levels of NGF, BDNF, NT-3, and NT-4 in AD patients, whereas viewing the weather information video failed to do so. In contrast, viewing the humorous video or the weather information video had no effect on these parameters in normal subjects. Collectively, laugher caused by viewing the humorous video reduced stress levels with a concomitant decrease in plasma neurotrophins in AD patients. These results may be useful in the study of neuroimmunology and treatment of AD.