Why does morning sunlight improve sleep?

Morning sunlight significantly improves sleep by regulating your body's circadian rhythm. When you expose your eyes to sunlight early in the day, it triggers several biological mechanisms that enhance wakefulness and prepare your body for sleep later. This natural light exposure increases the amplitude of your morning cortisol spike, which is crucial for energy, focus, and mood throughout the day. It also helps suppress melatonin, a hormone that facilitates sleep, aligning your body's internal clock with the day-night cycle 1 2.

Additionally, getting morning sunlight sets a timer for you to be able to fall asleep about 16 hours later. This light exposure is essential for regulating various bodily functions, including metabolism, and it serves to "wash out" residual adenosine, a compound that can promote sleepiness if it accumulates 1 3. Engaging in this simple practice of morning light viewing not only boosts your energy and mood during the day but also helps ensure a higher quality of sleep at night.