“…It was reported that psychological stress induced by performing an arithmetic or speech task inhibited forearm flow response, indicating endothelial dysfunction (Takahashi et al, ; Takeda et al, ; Toba et al, ). Previous animal experiments partially elucidated its mechanisms, demonstrating that stress hormones, such as glucocorticoids, endothelin‐1, and inflammatory cytokines, caused endothelial dysfunction through the impairment of NO‐dependent vasodilation (Ryu et al, ; Sanchez et al, ; Toda & Nakanishi‐Toda, ; Tokuda et al, ). A continuous reduction in stress by laughter therapy may improve endothelial dysfunction in older people via a reduction in glucocorticoids, as previous studies showed that serum concentration of glucocorticoids was significantly decreased in participants who viewed a humorous video compared to control participants (Eriksson et al, ; Ryu et al, ; Walter et al, ).…”