Biological effect of bright light

Abstract 1. 1. Five minute bright light exposures reduced plasma levels of melatonin in eight normal subjects. 2. 2. No significant change in ACTH levels occurred. 3. 3. These results raise the possibility that short intense light exposures can synchronize circadian rhythms as well as benefit patients with seasonal affective disorder. They also indicate that short pulses of bright light do not affect pituitary ACTH production.