How does blue light exposure affect melatonin secretion?

Blue light exposure has a significant impact on melatonin secretion, primarily by suppressing its production. Melatonin is a hormone that helps regulate sleep-wake cycles, and it is typically secreted by the pineal gland in response to darkness. When blue light, which is commonly emitted by screens from devices like smartphones, computers, and televisions, is detected by the photoreceptors in the eyes, it signals the body that it is still daytime. This leads to a decrease in melatonin production, which can interfere with sleep quality and the circadian rhythm.

This suppression of melatonin due to blue light exposure explains why it is often recommended to limit exposure to blue light in the evening, especially before bedtime, to promote better sleep. The other options do not align with the established understanding of how blue light affects melatonin levels: it does not enhance production, there is a definite impact (not no impact), and it does not cause an immediate spike in melatonin, which would contradict its role in promoting sleep when in darkness.