ADHD and Caffeine: Why Some People Use Coffee to Focus and What the Research Actually Shows

Why caffeine comes up

ADHD and caffeine get talked about together because so many people reach for a coffee or an energy drink when their brain just won't get going. ADHD medicines such as methylphenidate are stimulants, and caffeine is a stimulant too, so it seems logical that a strong coffee might do a similar job. You might even know someone who says coffee calms them down rather than winding them up. That's what people report, though, and the research is far less convincing.

Where caffeine hides

Caffeine isn't only in coffee. The NHS lists tea, cola, energy drinks, caffeine tablets, chocolate, guarana and some health or fitness supplements as sources. It puts about 100mg in a cup of instant coffee, 75mg in a cup of tea, 40mg in a can of cola and 80mg in a 250ml can of energy drink, and says filter and coffee-shop coffee can contain more. So a "focus" or pre-workout powder listing guarana adds to the caffeine you've already had.

What studies found

Most of the research is either small trials in children, many of them decades old, or surveys asking adults how much caffeine they have. Here's what the main ones show.

Trials in children

A 2023 review of randomised trials found seven studies comparing caffeine with a dummy pill in 104 children aged 5 to 15. Four found no improvement in any ADHD symptom. One found a change on just one of five rating scales, one found wider improvement, and one found better sustained attention but worse impulsivity. When four of the trials were pooled together, there was no real difference between caffeine and the dummy pill.

Surveys of adults

A 2022 online survey of 2,259 adults found no link between how much coffee, tea, energy drinks or cola people had and how strong their ADHD symptoms were. People with more ADHD symptoms did show more signs of problem caffeine use. A study of US Army soldiers found those with ADHD used more caffeine pills and energy drinks, and caffeine use was linked with fewer of some symptoms, but that kind of study can't show caffeine caused the difference.

Caffeine with L-theanine

L-theanine is an amino acid found in tea, and it often turns up alongside caffeine in "focus" supplements. One small study gave the two together to five boys with ADHD aged 8 to 15, and found better scores on some thinking and attention tests. Five people is far too few to tell you anything reliable, and a recent review of ADHD supplements said caffeine on its own showed no significant benefit.

Caffeine and medication

If you take a stimulant ADHD medicine, caffeine is worth thinking about. The NHS says methylphenidate can cause a small increase in blood pressure and heart rate, and it lists caffeine as a common trigger for heart palpitations. Tell your prescriber or pharmacist roughly how much caffeine you have, including energy drinks, caffeine tablets and pre-workout powders, and ask whether that's sensible alongside your medicine. Never use caffeine to replace or top up a prescribed dose.

Caffeine and sleep

The NHS insomnia page lists caffeine as one of the most common causes of poor sleep, and advises not drinking tea or coffee for at least 6 hours before bed. If you usually go to bed at 11pm, that makes 5pm your last cuppa. Set a daily phone alarm called "last coffee" for that time, and keep decaf or a caffeine-free drink in the cupboard so you've got something to reach for instead.

Energy drinks and under-16s

The government has announced that the sale of high-caffeine energy drinks to under-16s will be banned in England from April 2027, subject to Parliament. It covers drinks other than tea or coffee with more than 150mg of caffeine per litre, and the government estimates around 100,000 children in England drink these every day. If you've got a teenager with ADHD who leans on energy drinks to get through school, it's worth talking it through with them and their GP.

Before you try

Caffeine isn't one of the treatments recommended in the NICE guideline on ADHD, and the research doesn't show it helps ADHD symptoms. To see what it's doing for you, note every caffeine drink and its time for a week, alongside how you slept. If you're pregnant, the NHS says to have no more than 200mg a day. Speak to a GP or pharmacist before taking caffeine tablets or supplements, and keep taking any prescribed treatment as normal.