Does Caffeine Negatively Impact Sleep?

close up of coffee cup on table

Now that I have recorded my regular sleep for two weeks as a baseline, the fun of experimenting begins.

For each episode, I will be manipulating one variable and looking at the impact that it has on my sleep over a two week period.

I will then discuss what my data shows, how easy or difficult I found this strategy to implement, and what previous research says. My sleep data will be given a score out of 25, the applicability will be given a rating out of 25, and the science will be given a score out of 50. These three factors will then be combined for an overall score and grade for how effective the strategy is at helping people to improve their sleep

The first episode is on caffeine.

I usually don’t consider myself to be a big caffeine consumer, but as you can see in my baseline sleep diary data from the benefits of tracking your sleep article, I did have at least one caffeinated beverage on 10 out of the 14 days for the 2-week baseline period.

During this time, I slept pretty well, so it didn’t seem like small amounts of caffeine earlier in the day made too much of a difference in my sleep.

The Experiment

To really explore the effects of caffeine on sleep, I decided to be a little bit more extreme than what I usually am.

For the first week, I had absolutely no caffeine that I was aware of, including chocolate, soft drinks, tea, coffee or energy drinks.

For the second week, I had:

  • 50mg on day 1 (black tea)
  • 100mg on day 2 (instant coffee and dark chocolate)
  • 200mg on day 3 (Gloria Jean’s coffee and can of Red Bull zero)
  • 400mg (250ml of Red Bull and 1000ml of Monster energy drinks) on day 4
  • 200mg on day 5 (Gloria Jean’s coffee and can of Red Bull zero)
  • 100mg on day 6 (percolated coffee) and
  • 50mg on day 7 (can of coke zero).

400mg is much more than I would recommend for my clients to have on any given day. To make it even more interesting, I also had caffeine right before bedtime on days 3, 4 and 5. This is NOT RECOMMENDED to those who are trying this at home, especially if you have insomnia, are pregnant or are sensitive to caffeine.

The Outcome

Comparison 1: No caffeine vs baseline data

Without any caffeine, my sleep efficiency was precisely the same (96.4%) as the two week baseline period. When you consider that I was also on holidays and travelling down the great ocean road and spending time out in the sun and at the beach, this was a bit surprising to me. I thought cutting out caffeine would help more than it did. With no caffeine, I went to bed 20 minutes later, got out of bed in the morning 17 minutes later, spent 3 minutes less in bed each night, and slept 3 minutes less per night too, but was still getting the recommended 7-8 hours sleep on average. My sleep quality on a scale from 1 = terrible to 5 = excellent was 4.14, which was pretty good.

Objectively, I had a deep sleep on Jan 19 (18/1/17 on the sleep diary) and a terrible sleep on Jan 20 (19/1/17 on the sleep diary), even though I had no caffeine on either day. That means that something else seems to have a more significant impact on the quality of my sleep than caffeine.

Comparison 2: No caffeine (week 1) vs caffeine (week 2)

Looking at the caffeine data, there does seem to be a bit of a time and dose-response effect. My three worst nights on the sleep diary data for the caffeine week happened when I had more caffeine and when I had it right before bed.

Looking at the week as a whole, I spent 22 minutes less in bed per night with caffeine, went to bed 37 minutes later, woke up 15 minutes later, obtained 19 minutes less sleep per night, and was now getting less than the recommended 7-8 hours of sleep per night (6hours 47minutes). My time to get to sleep was pretty similar, however, and my sleep efficiency and time awake during the night were actually better on average with caffeine than without, as was my subjective sleep quality (4.29/5).

Objectively Jan 23 (22/1/17 on the sleep diary) was my deepest sleep yet, with over a 2:1 restful: light sleep ratio. This was with 50mg of caffeine that day. Even when I had 400mg of caffeine (including when I normally go to bed) on Jan 26 (25/1/17 on the sleep diary) my sleep was still more restful than light based on my Misfit Ray data.

Is Avoiding Caffeine a Good Sleep Strategy?


From my personal experience with this experiment, avoiding caffeine completely had no added benefit to my sleep in comparison to the amount that I normally consume. As it was neither harmful nor helpful I give the effectiveness of this strategy a 13/25.


It wasn’t too difficult for me to cut out caffeine from my diet, but I get how it may be for someone who is a regular coffee or tea drinker and really enjoys this as part of their daily routine. I know some people also find that it helps them to stay focused and productive at work and that it is a nice social pastime to share with friends and family. That’s not even getting into the people I know that adore eating chocolate on a regular basis and would find it extremely challenging to stop this daily treat. For their benefit, I’ll give the applicability of this strategy a 15/25.


The science suggests that too much caffeine can lead to increased cortisol and adrenaline levels, and therefore higher anxiety and stress during the day, plus higher arousal levels at night. Snel and Lorist (2011) found that it can increase wakefulness and counteract degraded performance related to sleepiness, but it can also cause irritability, headaches and dizziness. A lot of why people do perform better after caffeine is because they expect to perform better too. If the dose is too high, it can disrupt subsequent sleep quantity and quality (Snel & Lorist, 2011). There is also no nutritional requirement for caffeine in our diets. As a result, I’ll say that avoiding (or minimising) caffeine consumption is likely to assist more than harm sleep quality. I, therefore, give the science of the strategy a 30/50.

Overall avoiding caffeine as a way to sleep better gets a score of 13/25 + 15/25 + 30/50 =

58/100: Pass

The caffeine did seem to contribute to me staying up later and getting less sleep but didn’t seem to impair my sleep quality too much as long as I waited until I felt sleepy and then went to bed then.

It could have been quite a different story if I still tried to go to bed at my baseline time of 11:52pm rather than 12:49am, especially if I then became annoyed that I wasn’t sleepy or couldn’t get to sleep.

Arousal levels at night play a huge role in how likely we are to get to sleep, stay asleep and sleep soundly during the night. Caffeine does raise our arousal levels after we consume it, therefore it can impact sleep.

What I Recommend

Caffeine is not something that I spend a lot of time on in session with my clients. It is a part of good sleep hygiene instructions, which I include in my session one handout:

“Cut down on all caffeine products. Caffeinated beverages and food (coffee, tea, cola, chocolate) can cause difficulty falling asleep, awakenings during the night, and shallow sleep. Even caffeine early in the day can disrupt nighttime sleep.” – Perlis and Youngstead (2000)

I also include some information on how much caffeine is in certain products. If you aren’t sure how much caffeine you have each day, or how much caffeine is in a product that you consume on a regular basis, go to the website caffeine informer.

At caffeine informer, it tells me that my safe daily maximum is 650mg, and a lethal dosage of caffeine for me would be 16550mg. That means that even 400mg of caffeine is safe for me to consume in a day due to my height and weight, but it wouldn’t be for someone who is 65kg.

If you are interested, put in your weight, and figure out what the safe amount is for your health. Then tally up all of the caffeine products that you have in a typical day, and see if this is within the safe limits.

If you are wanting to have a consistently good night of sleep, divide this safe number by at least two, and minimise the consumption of caffeine as much as possible in the last 9 hours before sleep.

Why 9 hours?

Caffeine has a half-life of approximately 4.5 hours, which means that in 9 hours, 1/4 of the caffeine that you consume is still in your system. If you have a large coffee at 2pm that has 200mg in it, by 11pm you will still have approximately 50mg in your system, even if you can’t feel it. This may have minimal impact on sleep quality or quantity, as seemed to be the case with me, or it could have a more negative impact on someone who is particularly sensitive or reactive to it.

Based on my findings and what the science suggests, minimising caffeine consumption and having it earlier in the day is a good idea, but we probably don’t need to stop consuming it altogether.


If you struggle with sleep problems and have a bit of caffeine, that is okay. As long as you focus on winding down and relaxing before sleep and waiting until you feel sleepy before going to bed, you can get to sleep quickly and sleep well during the night. It is elevated arousal levels that keep you up, not the caffeine per se. People that stress out about the caffeine that they have had will sleep worse than those who consume a moderate amount of caffeine and don’t worry about it.

Thanks for reading! If you would like a personalised sleep report and the five things that you could do to best improve your sleep, please check out our services.

Published by Dr Damon Ashworth

I am a Clinical Psychologist. I completed a Doctoral degree in Clinical Psychology at Monash University and a Bachelor of Behavioural Sciences and a Bachelor of Psychological Sciences with Honours at La Trobe University. I am passionate about the field of Psychology, and apply the latest empirical findings to best help individuals meet their psychological and emotional needs.

3 thoughts on “Does Caffeine Negatively Impact Sleep?

    1. Hi jgillardosteo,

      My understanding is that if we have caffeine to artificially raise our cortisol levels in the morning then our body realises it is too high and won’t produce as much naturally over time, which makes us more dependent on caffeine to do what our body used to do by itself. It won’t impact our sleep that night, but it’s still potentially better to stay off it as much as possible in the first place.

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