Does Caffeine Negatively Impact Sleep?


Now that I have recorded my normal 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 score 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.

Normally I 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 to my sleep.

The Experiment


In order 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 jeans 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 jeans 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 in any given day. To make it 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 exactly 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 really deep sleep on Jan 19 (18/1/17 on the sleep diary) and a really bad 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 bigger 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 on 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.


Dr Damon Ashworth

Clinical Psychologist

9 thoughts on “Does Caffeine Negatively Impact Sleep?

  1. What an interesting read! Fantastic experiment to try – is this something you are continuing on with, changing other aspects of your schedule and diet to monitor any sleep affect? I think you alluded to that in the beginning of the post. As someone who has had sleep issues the bulk of my life I find things like this fascinating… and also because I adore coffee… when told I shouldn’t be drinking it because it might disturb my quality of sleep, I point out that I have had sleep issues long before my daily coffee consumption began, and insist that much of its effects are in fact mental, like a placebo effect. I’m happy to hear I wasn’t wholly incorrect 😉 Looking forward to more.

    Liked by 1 person

  2. I’m taking a psychology class right now and this topic is in one of the most influential case studies that we looked at in class. It was the study by Hobson and McCarley about the real source of dreams and their research led to the discovery that sleeping pills and the like repress REM sleep etc etc. Seeing the things you learned in practice is so exciting! Sorry, but I just got super excited. This is pretty interesting though. Now, I just need to figure out how to make a career out of it because this world is run by money… Why can’t we do things and learn things just because we’re curious? I digress…

    Liked by 1 person

      1. I’ve noticed that. Once you’re paid to do something, restrictions are imposed on you and you feel an obligation rather than an inquisitive inclination to pursue whatever you want to know and that kind of dampens your motivation. On that note, how does someone get “over-motivated”?

        Liked by 1 person

  3. Hi there. I recently began an online campaign aiming to help improve sleep quality amongst young adults. Similar to you, each week I explore a different sleep impairing activity. This campaign is based around a six-week challenge that promotes life style changes that are proven to reduce sleep impairment. It was very interesting to come across your blog as this week I have explored the impact of substances such as caffeine, alcohol and nicotine.

    I undertook a challenge of zero caffeine consumption to access whether this saw any significant changes. However, like you I generally don’t consume a lot of caffeine on a day to day basis so it has been difficult to make a fair assumption. I also proposed this challenge to my followers, so it will be interesting to learn of their experiences. I thought you may also be interested in their results, so feel free to check out my blog!

    I also would love to hear your feedback or any tips you may have to help my campaign. I have become very passionate about this topic and have already learnt so much. It’s great to see other people who share an interest. I am looking forward to reading your next post.


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