Human Melatonin Suppression by Light is Intensity Dependent
Version of Record online: 30 JAN 2007
Journal of Pineal Research
Volume 6, Issue 2, pages 149–156, April 1989
How to Cite
Mclntyre, I. M., Norman, T. R., Burrows, G. D. and Armstrong, S. M. (1989), Human Melatonin Suppression by Light is Intensity Dependent. Journal of Pineal Research, 6: 149–156. doi: 10.1111/j.1600-079X.1989.tb00412.x
- Issue online: 30 JAN 2007
- Version of Record online: 30 JAN 2007
- Received January 29, 1988; accepted June 17, 1988.
- low light intensity;
Five intensities of artificial light were examined for the effect on nocturnal melatonin concentrations. Maximum suppression of melatonin following 1 hr of light at midnight was 71%, 67%, 44%, 38%, and 16% with intensities of 3,000, 1,000, 500, 350, and 200 lux (lx), respectively. In contrast to some previous reports, light of 1,000 lx intensity was sufficient to suppress melatonin to near daytime levels, and intensities down to 350 lx were shown to significantly suppress nocturnal melatonin levels below prelight values. On the basis of these data, it is suggested that when examining the melatonin sensitivity of patient groups (such as bipolar affective disorders) to artificial light, an appropriate light intensity should be established in each laboratory. Light of less intensity (e.g., 200–350 lx) may be more suitable to dichotomize patient groups from control subjects.