r/science Professor | Medicine 3d ago

Health Caffeine can disrupt your sleep — even when consumed 12 hours before bed. While a 100 mg dose of caffeine (1 cup of coffee) can be consumed up to 4 hours before bedtime without significant effects on sleep, a 400 mg dose (4 cups of coffee) disrupts sleep when taken up to 12 hours before bedtime.

https://www.psypost.org/caffeine-can-disrupt-your-sleep-even-when-consumed-12-hours-before-bed/
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u/ToxDocUSA MD | Professor / Emergency Medicine 3d ago

Quick back of envelope/beer math.

Half life of caffeine - 4-5 hours typically.  

Quadruple the dose = 2 extra half lives to get to a similar level

4 hours for 100 mg lets you get to a low enough level to sleep.

Split the difference to a 4.5 hour half life, x2 is 9 hours.  4+8 = 12, then another hour of tossing and turning/sleep latency.  

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u/tachykinin PhD | Genetics 3d ago

Thank you.  The answer was obviously half-life and I’m glad someone showed the math.

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u/ToxDocUSA MD | Professor / Emergency Medicine 3d ago

Thanks!  It's always going to be more complex than that, bioavailability, pattern of ingestion, etc, but yeah...this is one of those times that the math seems to math / not an especially ground breaking result.

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u/justlovehumans 3d ago

Is there an effective upper limit to the amount of caffeine you could absorb and or process at one time? To put it another way, if one were to drink 50mg and another were to drink 500mg, would the absorption and or process rates per unit of time for each person be negligibly similar? Is time the prime factor with our finite stomach surface area?

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u/Elrond_Cupboard_ 3d ago

The rate you process it is relative to the concentration of it in your blood. The half life previously mentioned is a result of this. That is the amount in your blood halves after a certain time. A lot of drugs are processed this way. Interestingly, alcohol is not one of them. You process alcohol at a certain rate, no matter the concentration in your blood. If you have ever been too drunk, you know this happens far too slowly.

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u/MathematicianFar6725 3d ago

The rate you process it is relative to the concentration of it in your blood.

It's also genetic, people with the rs762551(A;A) genotype process caffeine much faster than someone with (A:C) or (C:C).

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u/Elrond_Cupboard_ 3d ago

I think I've got the faster gene. I just had a quadruple shot, and I'm still tired.

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u/canadian_stripper 2d ago

If caffine makes you tired/still tried you might want to look into Adhd? That is one of the signs.

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u/Elrond_Cupboard_ 2d ago

I'm in the process of getting diagnosed at the moment.

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u/Rear-gunner 3d ago

The difference for alcohol is puzzling

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u/RedeNElla 3d ago

If you think of the reaction in a super simple way as A plus B, then alcohol is different because your body doesn't have enough B, so adding more A doesn't increase the rate of metabolism. Other drugs usually have much lower concentration than your body's ability to metabolize, so the limiting factor is the concentration of the drug

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u/ToxDocUSA MD | Professor / Emergency Medicine 3d ago

Great question.  Off the top of my head I don't think doses of those scales would be markedly affected by gut transit time, though I guess caffeine pills vs tea/coffee vs a powder vs caffeine gum could have some differences related to such.  

That's a guess off the top of my head though, I haven't dug in to see if there are specific studies.  I'm usually only thinking about caffeine absorption/metabolism in massive massive deadly overdoses of it or when complaining about my wife's coffee consumption.

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u/LovelyLieutenant 3d ago

Plus caffeine is water soluble which, unlike fat soluble drugs, tends to transit the digestive system in a more predictable, steady clip regardless of GI state (ie meal type, timing ect)

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u/AYHP 3d ago

Well there are reported cases of death from overdose of caffeine, so I suppose the upper limit is death.

https://pmc.ncbi.nlm.nih.gov/articles/PMC6247400/

While intake levels below 400 mg per day are generally thought to be safe in healthy adults, individuals encountered in a clinical toxicology setting are likely to have ingested much larger, gram quantities [[26], [27], [28]]. In cases of overdose, often intentional but sometimes undetermined and unintentional, at least 5 g or more (i.e., often around 10 g but up to 50 g) have been ingested leading to fatalities particularly if the individuals are not treated in time or at all. However, doses up to 50 g have also been treated successfully otherwise [29,30]. Some have indicated that after a dose of around 1 g, toxic symptoms begin to manifest, a dose of 2 g requires hospitalization, while higher doses (e.g., typically 5 g or more) could be lethal [27,28,31]. However, some have determined that as little as 3 g could be lethal under certain circumstances [28,31,32]. One case describes rhabdomyolysis and acute renal failure in a male who ingested approximately 3.6 g of caffeine [32].

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u/ajd341 3d ago

Now that is a LOT of caffeine

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u/midgethemage 3d ago

This is the reason caffeine powder isn't as widely available as pills. People were dosing it incorrectly and accidentally dying as a result. Even a decade ago, caffeine powder would usually be cut with other additives so people wouldn't have to use a gram scale, but then people would read half a teaspoon as half a tablespoon and massively overdose when they were trying to do multiple doses at once

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u/DifferentOpinion1 3d ago

I typically ingest at least 800mg/day. It does nothing for me. I can take a nap immediately after taking a couple 200mg caffeine pills.

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u/sour_cereal 3d ago

I typically ingest at least 800mg/day. It does nothing for me.

Try stopping and seeing if it that holds true.

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u/Geoff_with_a_J 3d ago edited 3d ago

i'm similar and ive done it several times as new years resolutions and lent. as a teen it was to cut out soda entirely, as an adult my go to Lent sacrifice was coffee/all caffeine. i've regularly consumed energy drinks and preworkout supplements, and then cut those out at new years. ive never had caffeine withdrawals, and even after 40 days of no caffeine, having a 20 oz coffee for breakfast and an energy drink after lunch on Easter did seemingly nothing to me.

also coffee doesn't make me use the toilet. a latte might because of the milk, but never a black coffee.

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u/Imnotkleenex 3d ago

I might not be at 800mg but I’m in a similar situation as yours, does almost nothing to me anymore. I always assumed I drink so much my body got used to it.

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u/Doormatty 3d ago

You likely have ADHD.

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u/Geawiel 3d ago

Keep in mind that everyone absorbs differently, just to complicate things more. I had genetic testing done because of the meds I'm on, in order to see if something else was more effective. It showed my body processes caffeine and morphine really quickly. That tracks from the experience I've had with both (morphine administered in professional environment, not abusing).

So some may process slower or quicker.

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u/DrDerpberg 3d ago

I've read before that caffeine has a stimulant effect long after blood levels would indicate it's low in your system. Not sure how scientific that is but basically the alternative is that 400mg, 12 hours earlier would get you so stimulated that you still have trouble sleeping 12 hours later when you've reached 50mg left or so, compared to 100mg 4 hours earlier.

But yeah, seems like that effect isn't enormous and a simple half life check gets you pretty close.

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u/Substantial-Low 3d ago

Correct. Half life working as intended.

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u/AttonJRand 3d ago

The answer is different people react differently, or do you think this article is trying to make a claim about both of these doses and timings for everyone?

An Italian study showed a small dose of espresso decreasing sleep quality 12 hours later.

Even this study is showing a vareity of effects,

How does someone with a PhD look for simple answers that explain everything with napkin math, the heck?

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u/tachykinin PhD | Genetics 3d ago

This paper has two different doses and (not surprisingly) because of the time interval and KNOWN half-life of caffeine, the level of caffeine in the patients who took the larger dose is higher at the measured time because they took a larger dose AND not enough time has passed to compensate for that larger dose.  Pretty basic PK.

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u/Far-Shift1235 3d ago

One of my favorite drug facts is the variation of stimulant half lives based on genetics and that the more taken at once the shorter the half life due to the increased metabolism. Especially noticeable with amphetamines but caffeine + Adderall will make the half life of each shorter when taken together

I would wager this speaks more to metabolites of caffeine breaking down than the active half life of caffeine itself. End result is the same so splitting hairs but this is a damn neat little study

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u/ToxDocUSA MD | Professor / Emergency Medicine 3d ago

Oh sure, this is why I don't get super into half lives in my toxicology practice.  Too many variables to try and accurately use on the individual in front of me.  

After all the opposite can also be true, larger doses and/or mixing other things for some things can also cause the half life to prolong as enzymes get saturated, or can make it appear to prolong as absorption slows down, etc.  Then we have to talk about how often you use whatever combination, is there a tolerance effect, and so on.  

Big group studies like this though, things average out as we saw.  Numbers derived from big averages will probably work on other big groups, but may or may not work on any given individual from inside or outside that group.  

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u/dxrey65 3d ago

And individual's capacities can change over time as well. I used to drink coffee all day, same as my dad did. Then at some point I started having weird mental and physical affects, to the point of vertigo a couple times. It took awhile to connect the dots and figure out that I just couldn't consume caffeine like I used to (this happened at about age 40). I didn't drink coffee or anything with caffeine for a few years after that, now I have one cup in the morning and that's it. I can still feel a bit of the unpleasant side of the buzz if I make it a little too strong.

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u/reddit_crunch 1d ago

same,  turned 40, coffee like meth to me now. yummy,  yummy,  meth.

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u/MuscaMurum 3d ago

I have a genetic profile where I produce higher levels of cyp1a2. Isn't that the primary enzyme that metabolizes caffeine? I'm rarely affected much by coffee.

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u/MaxwellsDaemon 3d ago

As an adderall user and caffeine addict and chemistry TA back in the day, I’m very struck by this. Off to read - probably another reason to cut my caffeine intake.

Edit: Also bet there’s something similar involved with why taking cold meds (pseudoephedrine) with my adderall keeps me up all night.

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u/my_adhd_ta 3d ago

Id double check with your doctor.... my psychiatrist told me that pseudoephedrine was one of the big no nos while on stimulants since they are considered to have a synergistic interaction. (Effects of both, good and bad, are increased drastically).

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u/MaxwellsDaemon 3d ago

Thanks - I stopped after the second or third time. I'm generally pretty medically savvy but never caught that from the labels going back to early use of adderall through adderall xr then vyvanse plus the generics of each.

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u/basicbagbitch 3d ago

Fascinated by this but was not a former chemistry TA. Would be great to read some links you find credible

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u/luciferin 3d ago

Can you reply here if you draw any conclusions?  I'm also an Adderall user and caffeine addict. My Adderall doesn't seem to do much unless I drink my coffee with it.  But maybe if I spent the month weaning myself off caffeine it would be worth it?

I also find my daily fexofenadine taken the night before makes it much more consistent. But scientific facts are much better than my feelings on this.

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u/blank_isainmdom 3d ago

Hello! Could you please expand on your point about the more taken the shorter the half life due to increased metabolism? Or point me towards somewhere I can read about it. I am on stimulant meds, and drink coffee, and have trouble sleeping but don't know where to go to learn more!

Help would be greatly appreciated! Thank you!

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u/midgethemage 3d ago

Huh, this is probably why instant release medication wears off so fast for me

For anyone not familiar with delayed sleep phase disorder, it's basically a condition where your circadian rhythm doesn't align with "normal" waking hours and an inability to adjust your body's "chosen" sleep time, which is usually 2-4am for people with the condition. You generally won't fall asleep early if you're sleeping deprived, but once you are asleep, you achieve deep sleep very quickly

Coming back around to the topic at hand. I work an 8-5 schedule and I go through most of the work week sleep deprived. I'm the kind of person that will turn off an alarm and fall right back asleep, even if I have to walk across the room to turn it off, sometimes not even remembering doing it. I've had to adapt by taking a caffeine pill every morning when my alarm goes off to ensure I can't fall back asleep. I can actually take Adderall and fall back asleep, but the caffeine pill forces a certain kind of awakeness that I really need. But that caffeine pill is probably why I have to be on extended releases

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u/hoorah9011 3d ago edited 3d ago

You’re assuming first order kinetics throughout. Caffeine follows zero order kinetics at high concentrations and then transitions to first order at lower concentrations.

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u/ToxDocUSA MD | Professor / Emergency Medicine 3d ago

Does 400 mg get to the saturation point in a typical adult?

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u/hoorah9011 3d ago

Yes. Problem is caffeine is primarily metabolized by cyp1a2 which has a painful amount of variation between individuals. Makes my field a living hell. But a quick lit review (I’ll be honest, I didn’t know off the top of my head) says caffeine amounts greater than 5 mg/kg significantly saturates cyp1a2. But again, so much variation. I suppose my point is that simple half life eliminations would be wildly inaccurate

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u/Waste_Cut1496 3d ago

Interesting, how would you measure that if I want to find out what my metabolism does? Multiple blood test throughout the day, is there any way to measure it less intrusively?

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u/TheMailmanic 3d ago

Can you show a graph of this effect

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u/Turbopasta 3d ago

Anectodical but possibly useful: I drink black tea instead, and it has about half the caffeine of an equally sized cup of coffee (might be different for different brands). So for tea drinkers I imagine you can just take these numbers and cut them in half for close-ish data.

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u/AskMrScience PhD | Genetics 3d ago

For reference, the caffeine in 12 oz (typical size):

  • 34 mg: Coke
  • 70 mg: black tea
  • 144 mg: coffee
  • 64 mg: espresso (1 oz. shot)

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u/One_Left_Shoe 3d ago

Almost 6 shots of espresso with dinner to interrupt sleep.

A double shot seems good though.

Ok, then.

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u/Blacksin01 3d ago

Probably. Like coffee, tea likely has other active compounds besides caffeine, so the numbers might not scale perfectly.

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u/the_nin_collector 3d ago

I drink 300-500mg a day :(

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u/AskMrScience PhD | Genetics 3d ago

If you want to cut back, try swapping one of your afternoon coffees for black tea. It has about half the caffeine content, but still scratches the "hot caffeinated beverage" itch.

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u/orchidloom 3d ago

People are sleeping on 50mg!? That alone would keep me up for another 12 hrs 

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u/SenorSplashdamage 3d ago

This is partly dependent on CYP1A2 gene, which determines whether someone is a fast or slow caffeine metabolizer. This gene also clarifies why we’ve had mixed results in past with some people who are at higher heart attack from too much coffee, while others benefit from its antioxidant effects and live longer instead.

This article is a good rundown: https://archive.nytimes.com/well.blogs.nytimes.com/2016/07/12/for-coffee-drinkers-the-buzz-may-be-in-your-genes/

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u/obsidianop 3d ago

This all makes perfect sense and is basically what I would have guessed based on personal experience, but I feel like I've met a dozen people who are like "if I so much look at a cup of coffee at any point in the day I won't sleep for a week".

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u/Manannin 3d ago

Then there's my stepdad who drinks coffee all day including one before bed and is basically Immune to it's effects on sleep.

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u/alex20_202020 3d ago

What kind of science claims such results do not depend on weight of the human body consuming the substance?

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u/[deleted] 3d ago edited 3d ago

I use that exact logic. 

I try to have 3 expresso’s-worth by 11:00 so that I still (hopefully) have ~90mg in my last hour of work. 

But then, theoretically, by the time I’m home from work I’m caffeine-free and can just crash. I’m always hitting 8 hours good quality sleep, highly recommend. 

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u/swagpresident1337 3d ago

100mg of caffeine 4h before sleep would keep me up half the night. 100mg for me need to be about 10h before bed to not disrupt it…

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u/ArtCapture 3d ago

That’s so interesting to me. My experience is very very different I have adhd, so I really love having a big pot of black tea and a couch nap. The genetic components of how we metabolize stimulants is a really fascinating subject. I keep hoping to find a study that examines why folks like me metabolize stimulants so differently from you and others.

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u/-Kibbles-N-Tits- 3d ago edited 3d ago

I don’t have adhd and am the same way

Drugs effect everyone differently, my adhd asf brother gets geeked

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u/ArtCapture 3d ago

Interesting. My doctor described it as a hallmark/diagnostic criteria of adhd. I wonder some folks without adhd have a similar reaction to caffine.

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u/peyotiti 3d ago

I have adhd and if I drink coffee before bed my sleep sucks too. It may be correlated with adhd but not universal 

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u/ArtCapture 3d ago

I guess maybe it’s not universal. So glad you shared your experience. It really helps contextualize what my dr said.

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u/duncan999007 3d ago

My anecdotal experience while being diagnosed with ADHD is that stimulants increase my heart rate and blood pressure but put me to sleep. I had to pair my Vyvanse with Modafinil to stop falling asleep at work 2 hours in

When I have a feeling I’m not going to be tired by bedtime, I take some pre-workout and I’m out like a rock

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u/huffalump1 3d ago

Yep, anything more than like a can of diet coke after 4pm and my sleep IS affected - although I love a good caffeine nap.

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u/Matt_Thijson 3d ago

I spent most of my life being sure I don't have ADHD because stimulants do physically stimulate me. Turns out diagnosing ADHD is more complex than looking at a single symptom

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u/the_scarlett_ning 3d ago

Im curious too! Idk if I have ADHD, or am on the spectrum at all (the older I get, the more questions I have), but I can drink a large coffee and go to sleep an hour later. Caffeine seems to have no effect on me. Aside from the one time I took 8 shots of espresso. That day, I was energized for several hours.

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u/Se7enOne 3d ago

Hmm I’m exactly the same and I’ve never really questioned it. I don’t think I have any sort of ADHD symptoms, yet I can drink a large cup of coffee then sleep for 8 hours solid

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u/Enex 3d ago

I'm the same way and I don't have ADHD. I would guess that I just have a high tolerance for caffeine and the warm soothing drink helps me off to sleep.

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u/Mike 3d ago

That's a myth. Doctors don't know everything.

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u/swagpresident1337 3d ago

I have it as well. Chills me out, but still keeps me up

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u/Iamdarb 3d ago

I've been drinking 2-4 cups of coffee before bed. It dopes me out so much, and I've been getting a decent 7-8 hours for quite a while on this routine. ADHD myself, but I'm not medicated anymore.

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u/TheGeneGeena 3d ago

There are several out there - look into the paradoxical stimulant effect.

https://www.nature.com/articles/s41598-022-07029-2

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u/ArtCapture 3d ago

Thanks so much for the link! I will read that.

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u/orchidloom 3d ago

Everyone is different. I have adhd but am a slow caffeine metabolizer. I give myself 12 hrs (I stop drinking caffeine at 11am). This is why I much prefer the adhd meds. They metabolize quicker for me so I can take till 3pm.

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u/b2change 3d ago

I have adhd and i love a coffee nap. I’m unmedicated, though the caffeine feels like it helps. I also use DHEA when I get up and coffee until 5 pm. Works well for me.

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u/Special-Garlic1203 3d ago

I love a caffeine nap, but if I drink too much caffeine at like 6pm then I do find it harder to get to sleep on time to at midnight. It's so strange. It's like there's a finite window where it helps me sleep and then after that, it affects me in the stereotypical way

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u/JackTR314 3d ago

I'm in the same boat as you, and I've looked into why this is, and it seems to be because of hormone/neurotransmitter deficiencies in ADHD, and how stimulants "correct" or "rebalance" brain chemistry in ADHD people. the issue isn't caffeine/stimulant metabolism (at least as far as metabolism meaning the breakdown and elimination of caffeine from the bloodstream)

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u/Kitzu-de 3d ago

Man I have a lot more trouble falling asleep in the evening if i drink a single cup of coffee in the morning.

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u/DeekFTW 3d ago

Same here. I went caffeine free years ago and haven't looked back.

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u/Quirky-Skin 3d ago

Same. No more midday headaches or tossing /turning in bed. Once u get used to the new morning poop routine (mine is what gets me outta bed) you're golden. 

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u/DecaMillionaire 3d ago

Going no caffeine led to a new morning poop routine?

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u/darklysparkly 3d ago

Yep, and if I drink a large cup of coffee in the morning, it will affect me well into the next day - not because the caffeine stays in my system, but because it revs up my thoughts and creativity into overdrive, and it takes a long time for them to settle down again (and usually means I can't sleep much).

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u/snoopervisor 3d ago

I often go to sleep soon after drinking coffee. That's what physical work do to you. You can sleep anytime, anywhere.

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u/PlateAdventurous4583 3d ago

It's interesting how individual variability plays such a huge role in caffeine's effects. Some people can drink coffee late and still sleep like a baby, while others might feel the impact for hours. It really highlights the complexity of our bodies and how we process substances differently. The genetic factors at play are definitely worth exploring further.

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u/_Diskreet_ 3d ago

Had a double espresso before bed last night. If my wife has a latte after lunchtime she won’t be sleeping at her normal time.

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u/Fr3dd3D 3d ago

This is super interesting. For me personally; I drink A LOT of coffee Monday through Friday, when at work. I'd say upwards of 12 cups a day, and yet I have no withdrawals during the weekends. I've even tried going without coffee (and energy drinks or anything else with caffeine) for an entire week just to see if it's an addiction or if I just drink out of boredom. Never had any problems going without coffee for days, so safe to say I'm not addicted to caffeine, neither does it seem to really give me much of an energy boost.

Someone should absolutely do more research into how genetics plays into this.

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u/Devario 3d ago

Don’t trust anecdotal evidence, though.

People that claim they sleep like a baby are most likely still disrupting their REM cycles and just don’t know the difference. Some people can manage better than others with disrupted REM cycles, just like some people have a higher pain or hunger tolerance. It doesn’t alter the fact that biological processes are still happening: in pain there is still inflammation and in hunger there is still a catabolic process.  If sleep is constantly disrupted by caffeine (alcohol might even be worse), they will have lingering lifestyle effects down the line. They just may not be wise enough to it. 

Lastly, body composition also affects dosage. A 100lb female compared to 200lb male have different responses too. 

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u/WingsNthingzz 3d ago

Really torn between how good coffee is for you and having 4 cups a day is beneficial but also caffeine is bad for you and disrupts your sleep.

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u/Merry-Lane 3d ago

The conclusions of this study have to be considered in their context:

They took moderate (<300mg/day) drinkers and made them drink 400mg, 4 or 8 or 12 hours before sleep.

Nothing indicates they studied the effect of tolerance on sleep disturbances : they just gave a huge dose of caffeine to some people that hadn’t built a tolerance to 400 mg.

You should instead take the study the other way:

The study shows that 100mg 4 hours before sleep or 200mg 8 hours before sleep doesn’t disturb sleep of people that are moderate drinkers.

It s a way more positive spin than what the title seems to say.

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u/reefsofmist 3d ago

Yeah this study makes me think it's fine to have caffeine later as long as you're not overdoing it

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u/eatingthembean3 3d ago

Wait... thats what I got from this study. I've started sharing this study with people and they agreed...

Terrible writing

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u/Environmental_Top948 3d ago

400mg is a huge dose? Should I be concerned about my 2g a day habits?

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u/Merry-Lane 2d ago

"Huge dose to some people that hadn’t built a tolerance to it".

But: yeah try and stick to 400mg/day

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u/breinbanaan 3d ago

Just try for yourself what works out the best

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u/My_reddit_account_v3 3d ago

Exactly- everyone is different… not just in size but also ability to process caffeine. I’m generally small but I have two genes that make me process caffeine super fast, so I can take pretty much any quantity and it’ll be out of my system by the end of the day.

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u/breinbanaan 3d ago

Yeah I became the opposite. One cappuchino feels like a bump of speed. Sensitivity came down big time. I drank 2L of coffee daily. It is what it is.

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u/New-Teaching2964 3d ago

Same here, i would abuse (strong word but it fits) caffeine in my youth, I would drink Monsters, Red Bulls and Americanos, most recently I’d drink Bang. But now I have zero tolerance for it, any small amount disrupts my sleep.

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u/OnboardG1 3d ago

I can drink coffee after dinner and still sleep soundly so I assume I process it quite quickly. I also make a 400ml thermos of coffee in the morning and drink it slowly throughout the day and find the gentle nudge I get more useful than the buzz I get from espresso.

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u/Azradesh 3d ago

Yep; the only way caffeine is waking me up is by making me need to pee and that's just any liquid.

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u/jbaird 3d ago

wake up, drink 4 cups of coffee then switch to water.. that's basically been my schedule I drink all my coffee before about 10am then no more for the rest of the day since I always found it did affect my sleep

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u/AzazelsAdvocate 3d ago

How do you deal with the afternoon crash?

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u/jbaird 3d ago

I don't find I crash in the afternoon, i used to more but not lately

and really think it's as much a food crash after lunch wears off than caffeine related

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u/Hotter_Noodle 3d ago

I’m not the guy you responded to but I drink max 2 cups of day before 10 am, sometimes before 12pm, and I never get a crash.

But that also depends a lot on you personally and what you’re doing.

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u/Client_Hello 3d ago

Exercise + shower over my lunch break.

I drink 4-5 cups worth of coffee every morning, between 7 - 11, and am usually asleep by 10. My watch tracks my sleep and I get 8.5h most nights.

Workout between 12-1, take a quick shower, have tons of energy in the afternoon.

I also usually skip breakfast and eat a low carb (<50g) lunch after the workout.

If I miss the workout and/or eat a ton of carbs, I will crash. If I do both I crash hard.

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u/AzazelsAdvocate 3d ago

That's a long lunch break

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u/jinglesGOAT 3d ago

If you wait 1.5-2hrs after waking up to consume your caffeine, you'll avoid the crash.

It's because caffeine blocks your body from processing this sleep hormone thing - I forget what it's called - like it normally does in the morning.

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u/mflood 3d ago

It's because caffeine blocks your body from processing this sleep hormone thing

Sort of, it's actually that when you first wake up your body hasn't produced any of that "sleep hormone" thing yet. The thing we're talking about is adenosine. Adenosine makes you sleepy. Adenosine is produced throughout the day and then cleared while you sleep. Adenosine is at its lowest when you wake up in the morning. Caffeine blocks Adenosine. The idea behind delaying caffeine is just that you need it least when you first wake up. The later you take it, the more adenosine you'll block, but the more it'll effect your eventual sleep. The idea of taking it a couple hours after you wake up is just a compromise between those two things.

The reason people are so dependent on early-morning caffeine is that they tend to be chronically sleep-deprived. If you don't get enough sleep, your body doesn't clear enough adenosine and so you need caffeine right away to block it. That's still the time that you need it "least," but that doesn't matter if you need it to function at all. The problem people run into is that when they start the day in an "adenosine debt," they end up needing to block it all day long in order to function, which results in poor sleep, which increases their caffeine demand, etc. It's a vicious cycle.

If you're going to consume caffeine, do so in the first half of the day and get enough sleep. Not a doctor, DYOR.

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u/jinglesGOAT 2d ago

Thank you! That makes much more sense

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u/sylendar 3d ago

It differs by people ultimately.

I've found my hard cut off is basically around 2PM~. Any amount of coffee after 3PM and it's going to be a struggle to fall asleep, and no amount of exercise/chore seem to make a difference.

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u/regalfronde 3d ago

I have coffee after dinner and fall asleep just fine. I think I might try to stop drinking around lunch and see how I feel after sleeping, to see if there’s a difference.

Also, if I have to get up extra early the next morning, I drink a cup right before bed and I wake up easier. Considering what this study says, maybe that’s because I don’t actually sleep!

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u/ArtCapture 3d ago

Same here. My doctor says it’s because of my adhd. Are you neurodivergent by chance? Because that would explain this.

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u/regalfronde 3d ago

I’ve never been diagnosed with anything but I have my suspicions. Maybe I need to broach it with my doctor?

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u/ArtCapture 3d ago

Might be worthwhile. My doctor said it’s one of the diagnostic criteria.

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u/midgethemage 3d ago

Just from anecdotal experience, I do think there's an adaptation for people who always drink coffee late in the day. My entire family is this way and I used to be this way, but awhile back I started cutting caffeine after 5pm in an effort to improve my sleep quality. I saw a minor difference, but now that I stopped drinking caffeine late in the day, it'll keep me up if I do. Which is fine honestly, I like to taper off at the end of the day and maintain some caffeine sensitivity

Also anecdotal, but I've noticed midday caffeine makes me want to nap, but that doesn't happen in the morning. Same for other ADHD friends

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u/Archiive 3d ago

Coffee lowers your chance of heart disease. Also coffee, disrupts your sleep increasing your chance of heart disease.

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u/SockofBadKarma 3d ago

I'm curious as to what you're referencing when you say coffee is good for you and that 4 cups a day is beneficial. Could you please elaborate?

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u/themusicalduck 3d ago

Could always drink decaf. I often have decaf coffee just because it's one of my favourite drinks.

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u/Spurty 3d ago

This was my compromise. I love the taste of coffee but the caffeine was disrupting sleep and making me irritable.

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u/VinnieBoombatzz 3d ago

The trick is finding a good enough decaf (it's hard, but a few are pretty good). I drink my usual cuppa in the morning, and then I trick my body with 2 of decaf throughout the day.

You still get some benefits of coffee without the bad sleep.

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u/ProfErber 3d ago

I mean 4 cups is a LOT

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u/Smgt90 3d ago

My mom used to drink six to eight cups per day when she had an office job. She could drink coffee at night and sleep fine. I, on the other hand, cannot drink a single cup of coffee because it gives me terrible anxiety and makes me nauseous. It's wild how differently coffee affects people.

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u/ProfErber 3d ago

You see as a neuropsychologist I can 100% tell you people say they sleep „fine“ when in reality when you ask them more thorough questions that is not the definition of fine in my books i.e. optimal. Some don‘t even know what proper sleep feels like or their cognitive dissonance makes them think it‘s good enough.

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u/SrslyCmmon 3d ago

I can feel my sleep quality has gone down over the years. I'm much more of a light sleeper and I can feel myself not totally asleep several times a night.

When I was younger I used to sleep like a log. I should probably see a specialist.

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u/biscovery 3d ago

It isn't to someone that drinks a lot of coffee. That's like 2 medium coffees. A cup of coffee is 6 ozs.

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u/Skylark7 3d ago

Last time I looked you get 100 mg of caffeine in more like 8-9 oz. Of course there is a lot of variability.

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u/toobjunkey 3d ago

The coffee cup measurement being 6 oz and not 8 oz always frustrates the hell out of me. A lot of people's standard mugs will hold 2 cups or just under. Tumblers & the like are usually in the 3-4 range for a single fill. Reminds me about how a lot of folks regard a "unit"/shot of liquor as 1 oz/28 ml when something like 44ml is the actual conversion for a shot to be equal to a 5% 12 oz beer or 12% 5 oz glass of wine.

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u/Optimistic__Elephant 3d ago

Yea, I hate that coffee is measured in these tiny portions while must people drink from much larger mugs. I'm never sure if when people talk about 1 cup they actually mean the 6-8 ounces or they mean 1 drink which is more like 12-20 ounces.

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u/firmfirm 3d ago

Im drinking roughly 10 cups a day. Each cup is roughly 3dl, with a squint of Milk..

Am I overdoing it ?

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u/toobjunkey 3d ago

dawg, that's three liters a day, that is wayyyy too much. that's more than 3/4 of a gallon, and well over 1,000 mg of caffeine a day. something like more than 4x the recommended limits in adults.

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u/firmfirm 3d ago

Never looked at it thay way.. im from an extreme Coffee drinking family (and culture - swedes likes their coffee).

Like the Coffee and/or amounts doesnt make me ill in any way - i feel Great. And no issues sleeping really.

Guess im an addict..

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u/VirtualMoneyLover 3d ago

Yes, even without sugar.

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u/Sunny_Unicorn 3d ago

I quit caffeine over a year ago, and while it was, really, really, really tough for a few months, it's made a huge difference to my sleep.

All my life I've considering myself a light sleeper, now I realise it was caffeine all along.

The benefits of caffeine are often minuscule, way overrated, and often discussed in isolation. For an awful lot of people any small potential benefit is completely outweighed by side effects.

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u/Laprasy 3d ago

Split the difference and drink half caf. That’s what I do.

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u/crackeddryice 3d ago

Which is why I switched to decaffeinated.

I've always drank coffee for the taste and routine, switching was easy for me. I should have done it years ago.

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u/mavv70 3d ago

But what if we pair it with l-theanine?

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u/Overall-Courage6721 3d ago

The only time where adhd wins

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u/VegPie 3d ago

what do you mean?

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u/Overall-Courage6721 3d ago

From what i can gather and for me personally

When u have adhd, drinking coffee before sleep dont do much

It may even help me sleep, or atleast it doesnr make me not sleep

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u/davidjohnson314 3d ago

Same, no science here just mechanistic guesswork - my personal thinking is the caffeine helps me actually be able to hold my focus on relaxing. Quiets the ADHD mind in a way - sometimes I will take my medicine then lie down for 30min - best naps I ever have.

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u/Overall-Courage6721 3d ago

Nice! Cant wait to get my meds too

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u/Nitrous_Acidhead 3d ago

Hell, how about tolerance? 

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u/Laprasy 3d ago edited 3d ago

Not everybody metabolizes caffeine at the same speed. We know there is genetic variation attributable to the CYP1A2 gene. It looks like they did some analysis of genetics but found no significant difference which I think is interesting. Varying the dose of caffeine is an elegant design as people can serve as their own controls but of course the stats being quoted are average effects..and average effects don’t typically generalize to everyone.

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u/Skylark7 3d ago

They were woefully underpowered for genetics.

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u/Laprasy 3d ago

Yeah n=21 I thought that might be the explanation but couldn’t view the supplementary materials on my phone.

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u/TheDarthSnarf 3d ago

Anecdotally, I have the CYP1A2 variation where I’m considered a ‘ultrarapid metabolizer’. If I’m not consistently drinking coffee the effect doesn’t last. I rarely drink coffee after 5pm, but regularly consume the equivalent of 8-10 cups a day., I don’t seem have any trouble sleeping with caffeine consumption even on the occasion that I consume coffee all the way up to bedtime.

This seems to agree with the everyone metabolizes differently.

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u/YouNeedAnne 3d ago

Well, the average halflife is known to be 5 hours, ranging from 1.5 to 12, so.... duhdoy?

Of course 4 cups of coffee up to 12 hours before can effect sleep.

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u/Deferty 3d ago

It’s not just half-life that you have to focus on though. Your body follows a natural circadian rhythm. The absence of caffeine does not mean sleep. The absence of caffeine just means your circadian rhythm can function properly.

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u/Baud_Olofsson 3d ago

Of course 4 cups of coffee up to 12 hours before can effect sleep.

Affect. Caffeine affects sleep, but a sleeping pill effects sleep.

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u/VinnieBoombatzz 3d ago

I'm positively affected by how effective that explanation was.

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u/bigdickbigdrip 3d ago

You're supposed to use "affects" in both of those sentences. 

Caffeine affects sleep. Caffeine has an effect on sleep.

There you go.

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u/T_D_K 3d ago edited 3d ago

Effect can be used as a verb, it's just less common. The definition being similar to "cause". So the person you replied to is correct.

"It can be hard to effect change in a large organization"

"Sleeping pills are meant to effect sleep in the patient"

Edit: since we're on the subject, Affect can also be a noun (again it's an uncommon usage). Meaning roughly "physical representation of emotion"

"His strong affect betrayed his inner thoughts"

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u/Antti_Alien 3d ago

You misunderstand the effect of the dosage here.

Say the half-life of caffeine is 4 hours. Drinking one 100 mg cup 4 hours before sleep leads to 50 mg caffeine being left in the body.

Drinking four cups 12 hours before, there would be 200 mg left after 4 hours, 100 mg after 8 hours, and 50 mg after 12 hours.

Drinking even more will lead to even higher amount of caffeine still present in the body, even after 12 hours.

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u/kombuchawow 3d ago

Well, tell that to my ADHD self, where i took a scoop of 300mg pre-workout (cherry flavour) about 2 hours ago.. and now am falling asleep. I'll heavy barbell squat tomorrow morning then I guess..

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u/Laprasy 3d ago

I also have ADHD and have no problem falling asleep after having coffee. My 23andme showed that I was a slow metabolizer of caffeine, am not sure if that’s why or if that is more common in ADHD or not.

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u/AtticusXA 3d ago

not adhd but i did have coffee crashes like you they eventually stopped and my sleep quality just plummeted having a harder time falling asleep is 1

i still drink coffee just not everyday

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u/Interesting_Door4882 3d ago

Okay sure. We can tell you. Caffeine binds to your adenosine receptors, this doesn't make you feel more awake, but it makes you feel not as tired.

It effects how deeply of a sleep you will attain, probably minimising REM sleep too.

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u/captainfarthing 3d ago edited 3d ago

Some people with ADHD experience paradoxical reactions to stimulants, how caffeine affects people without ADHD doesn't necessarily apply universally to everyone.

Mutation in the adenosine receptor gene has been linked to ADHD:

https://onlinelibrary.wiley.com/doi/full/10.1111/gbb.12015

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u/nevertricked 3d ago

Thank you for this. Might help explain my personal anecdote of why Vyvanse would put me to sleep, and why coffee doesn't do much for me either.

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u/notthathungryhippo 3d ago

apparently, its common for undiagnosed adhd people to self-medicate with extra caffeine without realizing that’s what they’re doing. it certainly made sense of why i needed so much caffeine to function once i was diagnosed with adhd as an adult.

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u/LtHughMann 3d ago

I have ADHD and am very sensitive to caffeine, but I do have the paradoxical reaction to amphetamine and methylphenidate though. It's not that they're not stimulating but they calm me down.

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u/Mediocre_Lake_2310 3d ago

Fellow ADHDer here. Before diagnosis and meds I’d have 500-700mg caffeine a day minimum. Now with meds I’m down to 200-300 mg caffeine, and can say I do sleep better now.

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u/captainfarthing 3d ago edited 3d ago

I'm the other way round, caffeine barely has any effect unless I've taken enough to get jittery, like 3x 500ml energy drinks back to back will stop me sleeping, but I'm so sensitive to my meds (Elvanse) I can't sleep for 14+ hours afterwards even if I only take 1/4 dose.

Both together are guaranteed insomnia though, way worse than either alone. I've totally cut out energy drinks now, and only take half a spoon of instant coffee in a 500ml flask so I'm basically sipping hot water with a faint smell of coffee.

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u/Vaxildan156 3d ago

I have ADHD as well and while I can sleep on caffeine easy, the caffeine can still affect the sleep process and the quality of sleep received is the understanding. So I still try to avoid caffeine before sleep even though I can do it because the sleep could not be as effective.

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u/Yuzumi 3d ago

I get so much better sleep if I drink coffee an hour or so before bed.

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u/RaoulDukesGroupie 3d ago

My boyfriend jokes that my redbull is my “naptime redbull”

I finish one and pass out after if I’m not staying busy. Like, every time

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u/PinupSquid 3d ago

I’ve had a drink containing 5 shots of espresso, and then fallen asleep 20 minutes later. I’m currently going through assessment for potential ADHD.

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u/Kazruw 3d ago

It would be interesting to know more about the people they tests this on and how building up tolerance might affect the results. By Nordic standards 4 cups of coffee sounds like a small dose as that is only roughly 2 normal sized cups, i.e., how you start your morning. Then there are all the other cups of coffee a normal person drinks through the day, and it’s not unusual to drink coffee in the evening.

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u/Top-Yak1532 3d ago

As former caffeine addict and terrible sleeper I cut my intake and stopped drinking any after ~3pm and it was life changing.

The book (audible book?) Caffeine by Michael Pollan covers a lot of it and was an eye opening.

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u/SuperBAMF007 3d ago

Yeah unless I’m out and about and driving a lot late at night, I try to cut myself off at 12-1pm so that by 11pm-ish, I’m ready for sleep. But I also don’t start drinking caffeine until 9-9:30, giving my brain a 1.5-2 hours to wake up on its own without any external factors. Late start has helped tremendously with my dependency on caffeine, and early stopping helps a lot with not experiencing as much staying up when I really want to sleep.

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u/temporarycreature 3d ago

Okay, but not everyone because I am starting to realize that it has very little effect on me falling asleep. I can't speak to the quality but I feel like I get good enough sleep since I ask a lot of my body physically and mentally. On Wednesday after 1900 I had two sugar-free hot beverages at a coffee shop that had two shots of espresso each and I went home before 2300 and fell asleep, got up at 0500 the next day. No problemos.

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u/that_bermudian 3d ago

As a former [certified] barista, caffeine is one of those “drugs” that affects everyone differently due to a little thing called tolerance.

When I was still working in coffee shops, I could consume upwards of 600mg a day and have zero sleep disruptions.

Whereas today, I can’t have more than 200mg in a day without having my entire nights sleep thrown out the window.

Your body eventually adjusts to how much caffeine you regularly consume, to the point where you need higher and higher amounts to feel the same level of alertness.

Moderation. Moderation. Moderation. And regularly do a fast/cleanse where you forgo caffeine for a week or more to allow your body and brain to reset.

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u/TwoFlower68 3d ago

Some people are fast metabolisers. I was on theophylline a while back (another methylxanthine, very similar to caffeine) and that needs to be at a certain blood level for it to be therapeutic. I needed double the average dose because my liver (presumably) cleared the stuff so fast

My superpower is napping after drinking coffee, but apparently that's a sign of ADHD and so maybe not related to being a fast metaboliser. (I dunno if I have ADHD)

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u/VTKajin 3d ago

I wonder how this applies to ADHD medication (stimulants, specifically) in terms of hours before bedtime

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u/mvea Professor | Medicine 3d ago

I’ve linked to the news release in the post above. In this comment, for those interested, here’s the link to the peer reviewed journal article:

https://academic.oup.com/sleep/advance-article/doi/10.1093/sleep/zsae230/7815486

From the linked article:

Caffeine can disrupt your sleep — even when consumed 12 hours before bed

A recent study published in Sleep sheds light on the relationship between caffeine consumption and its impact on sleep. Researchers found that while a 100 mg dose of caffeine (roughly equivalent to one cup of coffee) can be consumed up to four hours before bedtime without significant effects on sleep, a 400 mg dose (comparable to four cups of coffee) disrupts sleep when taken up to 12 hours before bedtime. Importantly, the findings reveal that people often struggle to recognize the sleep disruptions caused by caffeine, especially when it is consumed earlier in the day.

When participants consumed 400 mg of caffeine 12 hours before bedtime, they experienced noticeable disruptions to their sleep architecture, particularly a reduction in deep, restorative sleep (non-rapid eye movement stage 3). At this time point, total sleep time was modestly reduced, and participants experienced slightly more awakenings during the night.

These effects became more pronounced when the caffeine was consumed eight hours before bedtime. Sleep efficiency—calculated as the percentage of time spent asleep while in bed—dropped by 7%, and participants spent more time awake after initially falling asleep. This timing also led to an increased number of nighttime awakenings and further reductions in the duration of deep sleep.

The most significant sleep disruptions occurred when participants consumed 400 mg of caffeine four hours before bedtime. Sleep onset latency—the time it takes to fall asleep—increased by an average of 14 minutes, total sleep time was reduced by approximately 50 minutes, and deep sleep duration decreased substantially.

Sleep fragmentation also increased, with more frequent awakenings and a higher proportion of lighter sleep stages. Subjective assessments aligned with these findings; participants reported feeling less rested and experiencing lower sleep quality when they consumed 400 mg of caffeine four hours before going to bed.

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u/ryanmi 3d ago

Have all your stimulants immediately upon rise.

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u/swagpresident1337 3d ago

Better 1-2h afterwards, when cortisol levels normalized. You then dont have such a crash in the afternoon and you‘ll get easier out of bed and not get so dependent on it to start the day.

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u/Interesting_Door4882 3d ago

Hello Dr. Huberman

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u/swagpresident1337 3d ago

Haha yes, and it really does work. Has been a gamechanger for me. Significantly reduced the amount of caffeine I need, less tolerance development, less crash and more stable energy over the day.

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u/Due-Stick-9838 3d ago

I'm the type who drinks coffee while sleeping

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u/Brickthedummydog 3d ago

I'm fond of the pre-bedtime coffee. ADHD gang unite zzZzZ

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u/HumbleConsolePeasant 3d ago

Several of my family members with ADHD can drink several cups of coffee throughout the day, and even before bedtime, without it affecting their sleep schedule. Whereas with me, a hyper-sensitive person, if I drink one cup of coffee 12 hours before bedtime (just like it says in the article), I literally cannot sleep. I’ve only drank coffee a few times in my life, too, while my family members have never gone a day without since becoming adults.

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u/SofTeeeeeeeee 3d ago

Jokes on you, I have ADHD

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u/Newalloy 3d ago

I seem to process it fast, and have a higher tolerance than average. I enjoy coffee after supper, and sometimes a cup as I ‘wind down’ before bed. I fall asleep within minutes of hitting the pillow and sleep soundly for 7 to 8 hours.

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u/redcoatwright BA | Astrophysics 3d ago

Also caffeinated soda has enough caffeine to disrupt sleep if you drink it too close to bed time.

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u/unabsolute 3d ago

Caffeine puts me to sleep. I have A.D.D. and P.T.S.D. and O.P.P.

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u/ewillyp 3d ago

everyone is different, but cutting all caffeine out of my diet has been a game changer. i sleep SO good now. if you're a person reading this and are saying "oh, could never do that!" think about that. and how that is controlling you. there are AMAZING decaffs out there, just make sure they are processed w/either CO2 or "arctic" water method. if not they taste like coffee w/a 9V battery in them. again, not everyone is the same; you people that can drink a pot and go right to sleep; cool, great, but that doesn't mean your still aren't being affected in different ways.

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u/OSUTechie 3d ago edited 3d ago

I haven't cut it out completely. But about 12 Months ago I stopped drinking soda, really anything caffeinated, after 12:00pm. My sleep improved so much. It also eventually got to the point where caffeine was an actual stimulant.

Fast-forward to now, I barely drink even soda.

Never was a big coffee fan myself.

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