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Caffeine & ADHD: The Potential Positive & Negative Effects, According To Experts

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ADHD is estimated to affect 2.5% of adults. And it's getting a lot of attention lately in regards to the unexpected ways it can affect women and adults in general. If you've been diagnosed, your doctor may have recommended a stimulant medication such as amphetamine dextroamphetamine or methylphenidate. These stimulants are some of the most commonly prescribed ADHD medications, which influence attention and behavior by boosting the availability of the neurotransmitters dopamine and norepinephrine in the brain. 

But caffeine is also a stimulant that influences neurotransmitters such as dopamine—which raises the question: Could ingesting caffeine in the form of coffee, tea, or any other source be a safe way to help alleviate ADHD symptoms, or would it just make things worse? And is combining caffeine with ADHD medication even OK, or is it potentially dangerous?

Below, we dive into the effects of caffeine on the body and brain, along with research and expert insight into the pros and cons of consuming caffeine when you have ADHD. 

Ways caffeine can affect the body.

If you've ever consumed coffee or tea in the morning, you're probably quite familiar with the physical and mental lift that soon follows. That's because coffee is a central nervous system (CNS) stimulant that's been shown to help enhance focus and concentration, banish fatigue, improve memory, and boost overall mental functioning—at least temporarily. 

Caffeine predominantly does this by acting as an adenosine receptor antagonist. Caffeine is similar in structure to adenosine, a chemical that binds to receptors in the brain and subsequently slows down the activity of neurons that produce attention-boosting neurotransmitters like dopamine. This has the effect of making us sleepy and less able to maintain focus. But when we consume coffee, tea, or energy drinks, caffeine binds to these receptors instead, which minimizes the impact of adenosine and thereby curbs its effects by indirectly increasing dopamine release

This is why caffeine in moderation can have positive effects on focus, attention, and energy. However, too much caffeine can lead to problematic side effects such as restlessness, elevated anxiety, rapid heartbeat, insomnia, headaches, dependency, cortisol and adrenal disruption, and more.

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Caffeine, ADHD, and focus.

Many people with ADHD have been found to "self-medicate" with caffeine. And because both caffeine and stimulant ADHD medications influence the brain's dopamine system (via slightly different mechanisms), some experts believe it's reasonable to experiment with caffeine as a way to help curb symptoms—although, there are crucial things to consider such as the dose, whether you take medication, and the severity of your ADHD.  

"Stimulant medications for ADHD work to increase the amount of the neurotransmitter dopamine in the brain by slowing down its reabsorption, thus promoting increased focus," says Uma Naidoo, M.D., a Harvard-trained nutritional psychiatrist and author of This Is Your Brain on Food. "Therefore, consuming stimulating substances like caffeine can have similar effects on those with ADHD. Modest amounts of caffeine have been shown to help improve focus, stimulate the mind, and clear brain fog. Individuals with ADHD benefit from this form of a 'brain boost' as it helps them to focus on completing each task at hand." 

Other experts agree that it may be effective, particularly if ADHD symptoms aren't too severe. "It can be an effective option for mild ADHD, especially if the person is not having negative side effects such as GI symptoms, cardiac symptoms, or sleep disruption," says Lidia Zylowska, M.D., a psychiatrist at the University of Minnesota Medical School and author of The Mindfulness Prescription for Adult ADHD.   

Research in the area of caffeine and ADHD is not robust enough to be conclusive—most has been done on animals or children, and some studies are quite old. But overall, it shows promise, and some experts have called for additional investigation into caffeine's potential therapeutic effect. Here's a sampling of the research to date: 

  • In a 2013 study published in European Neuropsychopharmacology, treatment with caffeine was found to improve memory and attention deficits, as well as normalize dopamine levels, in an animal model. 
  • In a meta-analysis from 2000, which encompassed all previous studies on the potential usefulness of caffeine in ADHD treatment for children, caffeine (regardless of dose) was found to be less effective than stimulant medications. But, compared to no treatment, caffeine treatment was associated with improvements in children's impulsivity, aggression, and hyperactivity, as well as improvements in parents' and teachers' ratings of the children's ADHD symptoms.
  • Low to moderate doses of caffeine are likely more beneficial than high single doses. Research suggests that caffeine has a curvilinear effect—meaning that caffeine's effectiveness for ADHD increases with an increased dose but only up to a point where it begins to drop off again. Based on the meta-analysis mentioned above, this dose may be around 150 mg daily for children, but optimal dosing and timing aren't yet known, especially for adults. "The side effects of caffeine will determine the dose for each individual," says Zylowska.
  • In studies from the 1970s, discussed in this 2014 literature review, researchers noted anecdotal accounts of subjects who responded beneficially to caffeine but not stimulant ADHD medications, suggesting that there may be genetic predispositions that make one treatment better than another for certain patients. 
  • Not all studies are favorable, though. According to Zylowska, some research has shown that caffeine can worsen inhibition in boys with ADHD, making them more likely to be noisy, jumpy, and generally disruptive.  

So, while it appears that there's real potential for using caffeine to alleviate certain ADHD symptoms, caffeine can affect individuals quite differently—so there's reason to proceed with caution, listen to your body, and consult your doctor if you plan to use caffeine as a tool to manage ADHD. 

If you don't tolerate caffeine, or if you abuse it, it could potentially make your ADHD symptoms worse. This is particularly true if you suffer from anxiety, which can be negatively affected by excessive caffeine consumption, and which happens to affect about 50% of adults with ADHD. Additionally, if your caffeine consumption interferes with sleep, it will likely cancel out any potential focus-enhancing benefits. "Especially if consumed later in the day, the stimulating effects of caffeine can prevent us from falling and staying soundly asleep, which can exacerbate feelings of brain fog and lack of focus during the day," says Naidoo. 

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Caffeine + L-theanine: A power pair with potential.

Caffeine's potential for side effects has prompted research into its combined effects with L-theanine—an amino acid found in green and black teas, which is noted to contribute to these beverages' purported calming and soothing health benefits. "Much like caffeine, this amino acid is shown to alter brain chemistry in a way that increases focus and clears the mind for reduced feelings of stress and anxiety," says Naidoo.

In a 2020 study, the combination of L-theanine and caffeine not only helped to improve the focus of boys with ADHD and reduce mind wandering but also improved their inhibitory control and prevented rash behavior. While both caffeine and L-theanine demonstrated cognitive benefits individually, the combination was even better at alleviating these ADHD symptoms. 

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"In practice, L-theanine can help with anxiety, so perhaps there is some modulation of caffeine's negative effects," says Zylowska. "But this finding has to be further studied, to say there's a real benefit to the combination."

Green tea, including matcha, generally has the highest levels of L-theanine, along with moderate amounts of caffeine. 

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Caffeine & ADHD medication.

Now, another big question is: How does all the information above change when a person is already taking (or plans to start taking) stimulant ADHD medication? The answer isn't super straightforward since the effects of stimulant medications and caffeine are highly unique to each individual, as are symptoms of ADHD.

But, because both are stimulants, we do know that combining caffeine and ADHD medications "can potentially put someone at risk for having more serious side effects such as cardiac overstimulation," says Zylowska. "However, some patients combine caffeine with medications and are able to tolerate it well—it often depends on the dose of each."

According to Zylowska, some people may space out caffeine and stimulant medication—for example, relying on a morning cup of espresso to get going and using their stimulant medication later in the day. "Many patients also spontaneously decrease the use of caffeine as they start stimulant medications," she says. "But if they don't, it is really important to monitor for the synergistic side effects." (This refers to the fact that caffeine and stimulant medications have a synergistic effect that increases the other's effectiveness, which could potentially increase problematic side effects.)

For a generally healthy person, consumption of up to 400 mg of caffeine per day is generally safe and tolerable. But this may need to be much lower depending on your personal tolerance and whether or not you are taking medication. (Check out this handy guide to caffeine levels in nine popular drinks.)

Also, if you're pregnant or lactating, please speak with your doctor about how much caffeine is appropriate for you at all times.

The bottom line.

Caffeine is certainly not off the table if you have ADHD—and it may even offer some benefits, thanks to its actions as a CNS stimulant. While research is far from conclusive, some studies suggest that consuming low-to-moderate amounts of caffeine can boost focus and alleviate problematic ADHD symptoms like impulsive behavior—although not as effectively as medication. These effects of caffeine may be even more beneficial when it's consumed along with the calming amino acid L-theanine, although more research is needed.

The way caffeine affects you personally will depend on a variety of factors such as your personal tolerance, whether you have another health condition such as anxiety or cardiovascular issues, whether you're getting enough sleep, and whether you're taking stimulant medication.

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