How the Homeostatic Sleep Drive Works

Sleep is controlled by two different processes in your body: your circadian rhythm and your sleep drive. These two processes help determine your ability to fall asleep and stay asleep and affect how awake or tired you feel during the day.1 Experts collectively refer to your circadian rhythm and your sleep drive as the two-process model of sleep.

Your circadian rhythm is your “biological clock” that responds to external cues in your environment, such as light, to influence what times you fall asleep and wake up.2

Your homeostatic sleep drive, also called sleep pressure or sleep load, is a process that increases your desire to sleep throughout the day. Your sleep drive can be thought of as a balloon that gradually fills up during your waking hours and then slowly deflates during sleep. The longer you are awake, the more the “pressure” builds, making you feel increasingly tired. While you are asleep, the pressure decreases, eventually making you feel less tired and causing you to wake up.3

Understanding how your sleep drive grows and knowing the factors that can weaken it may help you get a better night’s sleep.

What Fuels the Sleep Drive?

The sleep drive is powered by adenosine. Levels of this molecule are controlled by energy metabolism within cells.

Every cell in the body uses adenosine triphosphate (ATP) as its energy source. ATP consists of adenosine attached to three phosphate molecules. As the cell breaks off the phosphate molecules one by one, it gains energy that it can use to complete various tasks. Eventually, once all three phosphate atoms are removed, your body is left with just adenosine.4

This remaining adenosine forms the sleep drive. As adenosine builds up, it leads to changes in the brain: it slows the activity of brain networks that makes you feel more awake and turns on brain processes that make you feel tired.1

Overall, the longer you stay awake, the more energy your brain uses and the more adenosine accumulates to make you feel sleepy.

Sometimes, other factors can also ramp up your sleep drive. Large amounts of mental or physical effort can sometimes increase sleep pressure, causing you to feel more tired after a busy day. Additionally, when you’re sick, and your immune system is activated to fight off germs, it produces molecules that further increase your sleep drive and make you want to sleep more.3 5

Can You Harm Your Sleep Drive?

The sleep drive is based on natural processes in the body related to metabolism, energy, and brain activity. You can’t damage your sleep drive or turn it off. However, some things may temporarily weaken the sleep drive and make it harder for you to fall asleep.

Hyperarousal is a process that can occur when you are under a lot of stress. It can also be a symptom of post-traumatic stress disorder (PTSD). During hyperarousal, the brain creates stress hormones that activate brain pathways and make you feel more awake. These hormones can also cancel out the effects of the sleep drive.6 7

Caffeine may also affect your sleep drive. When you drink coffee, tea, or soda, caffeine molecules attach to adenosine receptors — proteins in the brain that are responsible for sensing and responding to adenosine. Caffeine blocks adenosine from interacting with these receptors, preventing it from triggering the sleep drive.8

How to Harness Your Sleep Drive for Better Sleep

To reinforce and strengthen your sleep drive, sleep hygiene practices can help. “Sleep hygiene” refers to basic sleeping habits that can help you get longer, higher-quality rest.

Many experts recommend going to sleep and waking up at the same time every day. 9 Sleeping in for several hours on the weekend may make you feel better rested in the short term, but it doesn’t give your sleep drive as much time to build up. You may then have problems sleeping later that night, causing you to feel tired for the next few days.

Waiting until you’re tired to lay down in bed is also a good idea for boosting your sleep drive. If you’re trying to go to sleep before your sleep drive has built up enough pressure, you’ll lay awake. On the other hand, waiting longer to go to bed or even occasionally depriving yourself of a little bit of sleep can make your sleep drive stronger, helping you fall asleep more easily.10 In the same vein, avoiding napping during the day helps increase your sleep drive so you feel more pressure to sleep later in the day.

Conclusion

Trying to sleep with a weak sleep drive is a common cause of insomnia and is something that Cognitive Behavioral Therapy for Insomnia (CBT-I) can help fix. CBT-I is recommended by sleep experts such as the American Academy of Sleep Medicine as the first treatment option for people having trouble sleeping.11

CBT-I can help you better understand how sleep processes work and learn how to change your attitudes and habits to strengthen your sleep drive and get better rest.

To see if CBT-I might be the right fit for you, fill out Dawn’s questionnaire to begin learning more!