Effect of a 15 minute light pulse on nocturnal serum melatonin levels in human volunteers.
Level 3 - non-randomized controlled study
Non-randomized before-after experimental intervention in healthy human volunteers
PubMed 2056432 · doi:10.1111/j.1600-079x.1991.tb00003.x
What was done
Healthy human volunteers of both sexes were exposed to a single 15-minute pulse of bright light (350 cd/m²) early in the evening during winter months. Serial blood samples were collected to measure the effect of the light pulse on serum melatonin and cortisol levels.
What was found
Melatonin levels were significantly but transiently suppressed by the 15-minute light pulse, while cortisol levels were not affected. The abstract provides no specific numerical values, baseline concentrations, or exact p-values.
Why it matters
It demonstrates that brief light exposure can acutely alter human melatonin suppression without inducing a systemic cortisol response.
Limits
The abstract does not disclose the sample size, exact participant demographics, or numerical data. There is no mention of a separate unexposed control group or randomized sequence.
Cited by
- context Turning on bathroom lights in the middle of the night signals morning to the brain and halts melatonin production.