Boyce P, Kennaway D J
Biol Psychiatry. 1987 Apr;22(4):473-8. doi: 10.1016/0006-3223(87)90169-7.
A study was carried out to determine the intensity of light necessary to suppress melatonin. Ten normal subjects were exposed to four light intensities of 1000, 1500, 2000, and 2500 lux for 2 hr on different occasions, and melatonin levels were measured during exposure. All light intensities suppressed melatonin significantly, but none do daytime levels, with 2500 lux appearing to be the most "potent."
