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ADHD and caffeine: why coffee can make you sleepy

Some people with ADHD feel calm or sleepy after coffee. We look at what the research says, including a 2022 study of 2,259 adults, and share practical tips on caffeine timing.

By Peak21 October 20267 min read

Caffeine can leave some people with ADHD feeling calm or even sleepy, and the likeliest reasons affect everybody: built-up tiredness, short sleep and the way caffeine wears off. Research on ADHD and caffeine is thinner than the internet suggests, and a 2022 study of 2,259 adults found no link between how much caffeine people drank and how strong their ADHD symptoms were. The most useful thing you can change is timing, and we cover how below.

In a 2022 study of 2,259 adults in Hungary, daily caffeine intake had no link with ADHD symptom strength (Ágoston et al. 2022).
In the same study, people with more ADHD symptoms reported more signs of caffeine use disorder, even though their symptoms had no link with how much they drank.
About 60% of 3,691 adults with ADHD at Dutch clinics screened positive for at least one sleep disorder (van der Ham et al. 2024).
UK food safety agencies say up to 400mg of caffeine a day is unlikely to cause adverse effects in adults, with a 200mg limit recommended in pregnancy (FSA).

What does caffeine actually do in your brain?

Through the day, your brain builds up a chemical called adenosine. The more of it there is, the sleepier you feel, and sleep clears it away again overnight.

Caffeine fits into adenosine's receptors, the docking points on brain cells, and blocks them for a while. In plain terms, it sits in the lock without turning the key, which is why a coffee makes you feel more awake (Examine).

The important detail is that caffeine holds adenosine back rather than removing it. The tiredness is still there, and it returns as the caffeine fades. Caffeine levels in the blood tend to peak within about two hours, and the time your body takes to clear half of it ranges from about three to ten hours, depending on your liver enzymes. Two people can drink the same flat white and have very different afternoons.

Why does caffeine make me sleepy with ADHD?

We could not find a study that directly tests whether caffeine makes adults with ADHD sleepier than anyone else. What does exist are three good explanations.

The first is sleep. In a 2024 study of 3,691 adults with ADHD at 46 Dutch outpatient clinics, about 60% screened positive for at least one sleep disorder (van der Ham et al. 2024). The most common, at 36%, was signs of delayed sleep phase, where your body clock runs late. If you start the day short on sleep, there is a lot of adenosine for caffeine to hold back, and you feel all of it when the caffeine wears off.

The second is how the lift feels. London consultant psychologist Dr Elena Touroni describes caffeine's effect on dopamine giving some people with ADHD a calm, grounding feeling rather than a jittery one, which can be mistaken for sleepiness (The Chelsea Psychology Clinic). The idea is reasonable, since caffeine's action on one type of adenosine receptor can help dopamine release, but it has not been tested directly in adults with ADHD.

The third is habit. The same clinic points out that regular drinkers build tolerance, so the same cup does less over time and the dip that follows is easier to notice.

Does caffeine affect ADHD symptoms?

A popular idea says people with ADHD drink so much coffee because they are self-medicating. In 2022, Ágoston and colleagues tested this with 2,259 adults in Hungary who had caffeine at least once a week. Each person reported how much coffee, tea, stimulant drinks, cola and caffeine pills they had, and filled in a standard six-question ADHD screening tool.

Caffeine intake, whether from coffee, tea, stimulant drinks, cola or all of them together, had no link with how strong people's ADHD symptoms were. The authors concluded that caffeine consumption was "not likely to represent self-medication" (Ágoston et al. 2022). People with more ADHD symptoms did report lower well-being and more signs of caffeine use disorder, which means finding caffeine hard to cut back on. One quieter finding is that tea drinking was linked with higher well-being.

The authors are open about the limits. It was an online survey of volunteers, it took one snapshot in time, and it measured symptoms rather than diagnoses. Even so, it suggests coffee is a habit people with ADHD share with everyone else.

How did coffee lead our founder to guayusa?

Peak's founder, Louie Syred, has ADHD. Here is his caffeine story in his own words.

"In 2019 I was working 18 hour days across time zones, with calls to LA partners at 10pm. My partner was pregnant with our son. I was drinking coffee to keep going in the day and alcohol to switch off at night. The alcohol made me negative and down. The coffee made me wired and anxious."

"Along the way I learned about neurodivergence and realised I'm ADHD, autistic and mildly dyslexic."

"Guayusa is the leaf that started it. I first drank it in 2020, not long after I quit coffee, and I couldn't believe how clear and steady I felt. I've drunk it every day since. It gives me a long, steady lift that coffee never did, and it's the reason Peak exists."

Louie calls that daily swing the coffee and alcohol loop, and as he sees it, Western society has been stuck in it for 400 years. Guayusa is a holly leaf from the Ecuadorian Amazon and a cousin of yerba mate. According to our supplier, Amazonian hunters call it the Night Watchman, because it keeps them alert while they sit still and wait at night. Our guide to guayusa tells the full story.

When is the best time to have caffeine if you have ADHD?

Timing matters as much as amount, and these habits suit most people, with or without ADHD.

Set a cut-off time. In a 2013 study, 12 healthy sleepers took 400mg of caffeine six hours before bed and lost more than an hour of measured sleep, and their own reports suggested they had not noticed. The researchers suggested avoiding caffeine after 5pm (Drake et al. 2013, via AASM).
Match caffeine to a moment. Have it before the part of the day you want to feel lifted for, such as deep work, a run or a gig, rather than topping up out of habit.
Check in two hours later. Caffeine peaks within about two hours, so that is a good time to notice how you feel. A week of simple notes will tell you more than any article.
Look at last night first. If caffeine leaves you sleepy, your sleep is the place to start.
Know your numbers. Adults can have up to 400mg a day without expected adverse effects, and 200mg is the recommended limit in pregnancy (FSA).
If you take ADHD medication, ask your GP, prescriber or pharmacist how caffeine fits alongside it.

How does Peak fit into the day?

Peak comes in two moods, so you pick how you want to feel. Calm is caffeine-free and made for relaxing at any stressful moment. Hype is the one with caffeine. Our guide to what a mood drink is explains the idea.

Hype is a berry citrus drink with 60mg of caffeine, all of it from 300mg of guayusa, plus 25mg of L-theanine. Your body makes dopamine from tyrosine, so we put 250mg in every can of Hype. High caffeine content. Not recommended for children or pregnant or breastfeeding women.

We built Hype around Louie's own daily ritual, and our line for it says it best: lifted, not wired. People open one before deep work, the gym or a night out, and a known 60mg makes it easy to plan around your cut-off time.

Meet Hype, made with guayusa and tyrosine.

Frequently asked questions

Is coffee good for people with ADHD?

The research gives no simple answer. The 2022 Ágoston study of 2,259 adults found caffeine intake had no link with ADHD symptom strength, while a 2022 review of animal studies found caffeine improved attention in animal models of ADHD, with unclear results for hyperactivity (Universitat Oberta de Catalunya). Studies in people are still limited.

Why do I crash after coffee?

Caffeine blocks adenosine, the chemical that makes you feel sleepy, without clearing it away. As the caffeine wears off, you feel the tiredness that built up in the meantime, and a short night makes it stronger.

Can you drink caffeine if you take ADHD medication?

This depends on your medicine and dose, so ask your GP, prescriber or pharmacist how caffeine fits with your treatment.

How much caffeine is safe in a day?

The Food Standards Agency says intakes of up to 400mg a day are unlikely to cause adverse effects in adults, and recommends a limit of 200mg a day in pregnancy (FSA).