The 'Caffeine Nap' Phenomenon Is Easily Explained By Science

Staying awake is a remarkably difficult task for a lot of us. Whether it is due to getting too little sleep or poor sleep hygiene, like sleeping with the lights on, many people do not get adequate sleep. Two of the most satisfying ways to lessen that daily grogginess are consuming copious amounts of caffeine and taking power naps. However, some have found that the combination of these things is the most effective, and neuroscience can give us some clues as to why. Essentially, naps and caffeine both work against a sleepy chemical called adenosine.

Cholinergic neurons release the neurotransmitter acetylcholine. This chemical messenger is incredibly important for promoting wakefulness and leads to the release of epinephrine and norepinephrine (also known as adrenaline and noradrenaline, respectively) from the adrenal glands. Adenosine inhibits cholinergic neurons, which can make you feel sleepy. As you are awake, adenosine builds up throughout the day, particularly during cases of sleep deprivation. Conversely, as you sleep, adenosine levels decrease in areas of the brain responsible for sleep and wakefulness.

Caffeine is a competitive antagonist of adenosine, meaning that caffeine binds to receptors for adenosine. Basically, caffeine blocks adenosine from activating the receptors, thereby preventing the neurotransmitter from beginning the downstream process that will inhibit cholinergic neurons. Think about caffeine behaving like a guard in basketball, stopping adenosine from sailing through the net. By hindering adenosine's ability to promote sleepiness, caffeine can help you feel more awake. But this effect is not immediate.

Caffeine and napping have two different approaches to combating the effects of adenosine. As mentioned above, sleep decreases adenosine, while caffeine competes with it. Therefore, pairing the two can have a synergistic effect on staving off exhaustion for some time. Moreover, a nap can help while caffeine takes the time to do its thing. After drinking a cup of coffee, it takes roughly 10 minutes before you actually start to feel an effect. That is a perfect amount of time to take a quick cat nap, which should not be any longer than 20 minutes. Then you can wake up feeling refreshed and, well, more awake.

For the best effect, it is important to restrict the time of rest. While a quick nap can help you feel refreshed, a long nap might leave you feeling groggier than before. If you fall into a deep sleep and are disrupted, that can leave you with some sleep inertia, which is that feeling you get when it's impossible to wake up to your alarm.

In some cases, people with attention deficit hyperactivity disorder (ADHD) report drowsiness after caffeine intake. While the neurobiological reasons for this are unknown, some hypothesize that this is caused by the effect that caffeine has on dopamine in the brain. Commonly, therapeutics for ADHD target dopamine signaling, particularly in the frontal lobe, which is the part of the brain where decision-making and cognition occur. This signaling is also impacted by caffeine because it is an antagonist of adenosine, which inhibits dopamine. Therefore, caffeine helps increase dopamine signaling by hindering the suppressive effects of adenosine.

Interestingly, stimulants tend to be helpful for individuals with ADHD, so some individuals have also reported behavioral benefits from caffeine intake. Of course, caffeine is not a substitute for pharmacological treatment, and some studies have found no overall benefit of caffeine, while others have described discrepancies in what constitutes a ideal dosage. Therefore, more research is required to understand how exactly caffeine interacts with ADHD, and whether it consistently induces drowsiness. Overall, it does appear that whether you have ADHD or not, a quick catnap after some coffee might make you feel a little more awake.