The Effects of Caffeine on Sleep

Caffeine’s Effect on the Brain

Caffeine is a neurostimulant, meaning it speeds up the brain.   Caffeine is also the most widely used addictive substance. It increases the brain’s pleasure and reward chemical dopamine, so you want more of it. It can also worsen stress and anxiety levels in many people without them being aware of it.

Most importantly when it comes to affecting sleep, caffeine binds tightly in the brain to something called adenosine, which is a brain chemical that makes us feel sleepy and slows down brain and nervous system activity.  Adenosine is like the brain’s ‘braking’ system.    Caffeine blocks adenosine and keeps us feeling more awake by removing those brakes.

What else has caffeine

It’s not just coffee that contains caffeine but also other substances such as: Tea, Chocolate, Energy Drinks and Matcha.  Tea has an amino acid called L-theanine which can slightly buffer the caffeine ‘jacked up’ effect but it doesn’t speed up how well or fast you can get rid of the caffeine so it’s not a license to consume more caffeine especially if you are particularly sensitive.

Caffeine sensitivity levels

It is very common for most patients to deny or be unaware of their caffeine sensitivity level and the only way to find out is, unfortunately, to wean down and then off caffeine completely for 4 weeks and monitor what happens to sleep quality and stress levels.

Your Enzymes that break down caffeine

There are specific enzymes in the liver that break down caffeine.  The one called CYP 1A2 handles most of the caffeine breakdown and how well this enzyme works and how much of it you have is highly individual.  That is why some people can get away with drinking coffee in the late afternoon and still sleep well (although many people who claim this in fact still do have some sleep dysfunction from caffeine when you really dig!) vs. others must limit intake to 1 cup first thing in the morning and staunchly avoid any source of caffeine after 11am to avoid sleep effects.  Some people cannot tolerate ANY caffeine at all without it disrupting their biological clock and sleep to some degree.

If you don’t break caffeine down as quickly as average, you can also be more prone to the negative effects of caffeine build up during the day, such as feeling more on edge, stressed or anxious. This is often only noticeable when you cut out caffeine for 1 month and track the difference before vs. after 30 days caffeine-free.

You can take a test to see if you are a slow or fast metabolizer of caffeine with a functional medicine doctor, but a caffeine holiday experiment works too and is free.

How Much Caffeine is bad for sleep?

How much caffeine affects you and your sleep is highly variable from person to person, due to huge genetic variation in how quickly and effectively your body can break down (metabolize) and get rid of (excrete) caffeine.

Sleep Quality, Deep Sleep and Caffeine

sleep QUALITY is affected not necessarily total sleep time or trouble falling asleep because that’s not typically how caffeine affects sleep the most.  Caffeine tends to affect our deep sleep, called Non-REM sleep, which happens a while after you fall asleep initially.  NREM sleep is actually the most important phase of sleep for replenishing your brain chemical peptides: such as your ‘happy hormone’ serotonin’ and the feel good/reward one called dopamine, and also needed to repair your cells, and get rid of bad cells or old cells (eg. prevent pre-cancer cells from multiplying etc).

The Delay effect on sleep

This delay effect on the sleep cycle from caffeine is the reason why if you want to take a power nap during the day of only 20minutes but want to avoid dipping into deeper sleep states (which can leave you feeling groggy and worse vs. more refreshed after the nap), drinking a small cup of coffee will allow many people especially if overtired, to fall asleep for that initial 20 minutes before the caffeine kicks in and jolts you awake before the deep sleep starts.  I however, do not recommend using caffeine for the naps on a regular basis because of the potential of it to affect sleep that night as well, even if used in the early afternoon.

Many people have been told by a well-meaning doctor that a bit of morning coffee/tea/caffeine wasn’t going to make any difference to sleep as long as they avoided caffeine ‘in the afternoon and evening.’  They are often told they have ‘treatment resistant insomnia.’   In most cases when caffeine is cut out for 4 weeks, their sleep noticeably improved.

Then, after the 4 week holiday they often try to re-introduce a single serving of caffeine in the morning. 8 times out of ten there is a negative response in the sleep pattern which can be a surprise to many.

How Caffeine affects each type:

For Exhausted:

Exhausted warrior types are the type most likely to have ultra sensitivity to caffeine so any caffeine must be removed for an entire month

For Wound Up:

Even 1 serving of caffeine can cause more ‘wind up’ in the nervous system without realizing it so any caffeine must be removed for an entire month


Because you tend to be a nighthawk, you may be having a cup of caffeine after midday or even later on. Cut out all caffeine after 10 am this month.


If you are a moody warrior but you also have some ‘wound up warrior’ features like having trouble relaxing or winding down for sleep it’s still very important to take a caffeine holiday. However, beware that your moodiness and irritability may get worse for the first week off caffeine until your brain adjusts. These symptoms should ease after a full 7 days on no caffeine

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