Is there a formula to a good night’s sleep? When we look at the process of sleep as the result of hormone functions, then we can say that the formula to quality slumber involves the complementary functions of melatonin and serotonin. Let’s look more closely at melatonin vs. serotonin and the different roles they play in sleep.
Melatonin vs. Serotonin: What’s the Difference?
To put it simply, melatonin is key to falling asleep, whereas serotonin is essential to wakefulness. While these two brain chemicals operate on opposite ends of the sleep-wake spectrum, their functions complement each other and impact the transition from sleep to wakefulness and from wakefulness to sleep. One can’t produce their intended result without the other.
Article at a Glance
- Melatonin and serotonin play different but complementary roles in the sleep process.
- Melatonin has long been established as the hormone that controls when the body sleeps and when it wakes up.
- Serotonin is associated with wakefulness, but animal studies have also found that deficiencies in serotonin are linked with sleep difficulties. Serotonin’s role in sleep is as a precursor for melatonin production and as a sleep-promoting chemical.
Melatonin, often referred to as the “sleep hormone,” is secreted by the pineal gland in the brain in response to environmental lighting cues. Melatonin levels increase when the environment gets darker and decrease when it gets lighter. The fluctuating levels of melatonin, as they coincide with environmental cues, help regulate biological rhythms, particularly the body’s circadian rhythms or 24-hour sleep-wake cycle.
When the sun sets, the pineal gland produces more melatonin to signal the body that it’s time to sleep; when the sun rises, melatonin levels decline to signal the body that it’s time to wake up.
What is Serotonin?
Serotonin is a neurotransmitter that performs multiple functions in the body; it plays a role in modulating mood, cognition, reward, learning, memory, and many other processes. It’s known as the “happy chemical”; low levels of serotonin is, in fact, associated with symptoms of depression. Serotonin is also a precursor to melatonin, which means that it is needed to produce melatonin.
Animal studies have found that serotonin plays a role in sleep, other than being a precursor to melatonin. The results revealed that the presence of serotonin is actually required “to get normal amounts of sleep.” However, these results seem to counter other findings which showed that serotonin production is at its peak during the day, when we are most awake.
Melatonin and Serotonin: How Do They Impact Sleep?
Experts have theorized that sleep is actually a function of complementary factors which involve both melatonin and serotonin.
- The circadian clock, which is regulated by melatonin, keeps the body awake during the day and tells the body to sleep at night.
- Homeostatic sleep pressure, which is the buildup of the pressure to sleep as the day goes on and the body gets tired. The release of serotonin during the day, which promotes wakefulness, contributes to the buildup of sleep pressure. Sleep pressure also increases when you don’t get adequate sleep at night, causing your body to feel tired even during daytime, when your circadian clock dictates that you should be awake.
Having a good night’s sleep, therefore, requires the alignment of the circadian clock (regulated by melatonin) with a high sleep pressure (which is influenced by serotonin levels, among others).
- The brain’s production of melatonin usually coincides with nightfall, or a few hours before bedtime. Melatonin levels decline as morning comes or right before waking time.
- The increase in melatonin levels signal the body to wind down and get ready for sleep.
- Light cues, both from natural and artificial sources, can impact melatonin production. Exposure to the blue light of your phone screen at night, for example, can delay or reduce melatonin production which, in turn, makes it difficult for the brain and body to go to sleep.
- High levels of serotonin are associated with wakefulness and low levels with sleep.
- Serotonin also helps you feel more energized; at the same time, it also plays a role in preparing the body to go to sleep.
- Studies have found that serotonin deficiencies may be linked to sleep disturbances, which further provides evidence that serotonin also has sleep-inducing properties. More specifically, serotonin contributes to the buildup of sleep pressure throughout the day.
Final Thoughts: Melatonin vs Serotonin
How well you sleep at night is influenced by many factors, including your daily habits, sleep routine, stress level, diet, and hormone levels. When it comes to hormones, sleep is a function of two complementary brain chemicals: melatonin and serotonin. Melatonin regulates the sleep-wake cycle by signalling the body when it’s time to sleep and wake up. Among its many functions, serotonin keeps you energized while you’re awake and contributes to the buildup of sleep pressure throughout the day; it’s also a precursor to the production of melatonin.
While there are key differences in the functions of melatonin and serotonin, having the right balance of these two hormones, therefore, is key to a good night’s sleep. Activities and environmental factors that disrupt this balance, one way or another, can result in sleep difficulties.