A team lead by Heo has found more evidence that seeing blue light, particularly at night, is energizing. The researchers “investigated the immediate effects of smartphone blue light LED on humans at night. . . . Each subject played smartphone games with either conventional LED or suppressed blue light from 7:30 to 10:00PM (150 min). Then, they were readmitted and conducted the same procedure with the other type of smartphone. . . . use of blue light smartphones was associated with significantly decreased sleepiness . . . and confusion-bewilderment . . . and increased commission error.”
J. Heo, K. Kim, M. Fava, D. Mischoulon, G. Papakostas, M. Kim, D. Kim, K. Chang, Y. Oh, B. Yu, and H. Jeon. 2017. “Effects of Smartphone Use With and Without Blue Light at Night in Healthy Adults: A Randomized, Double-Blind, Cross-Over, Placebo-Controlled Comparison.” Journal of Psychiatric Research, vol. 87, pp. 61-70.