L-theanine is an amino acid present in green and black tea. Some researchers believe it might explain the apparent health benefits of these teas for people with ADHD.

A group of small and inconclusive studies suggests L-theanine may improve attention and alleviate some symptoms of ADHD.

Many users anecdotally report improvements in concentration, performance, or attention span, and some small studies support these claims.

However, research into L-theanine is very new and incomplete. Therefore, experts do not recommend using it over standard ADHD therapies.

Although L-theanine is present in tea, it is also available as a supplement. Like all supplements, L-theanine is neither thoroughly tested nor strongly regulated, and there is no guarantee it will work.

Read on to learn more about L-theanine for ADHD.

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Some small studies suggest L-theanine may improve some ADHD symptoms, especially concentration and focus.

For example, a small 2020 placebo-controlled study assessed the effects of L-theanine on the ability to think in five boys with ADHD.

Brain scans of the participants showed changes in regions related to distraction, and the combination of L-theanine and caffeine improved scores on several cognitive tests.

Studies on L-theanine, though, have been very small. They are not large enough to draw conclusions about using it as a treatment, nor to prove that L-theanine works.

Additionally, because several studies have involved people already receiving treatment for ADHD, there is no evidence to support the idea that L-theanine can replace treatment when used alone. Instead, it may complement treatment.

One challenge of researching L-theanine is that teas containing caffeine are the main source of L-theanine.

Caffeine may be a confounding factor in some studies. Caffeine is a stimulant, and stimulants are a mainstay of treatment for ADHD.

Some animal research suggests caffeine may improve memory, concentration, and focus.

Some studies suggest L-theanine, especially combined with caffeine, may help with ADHD symptoms.

In a 2019 study with five male children with ADHD who responded to stimulant treatment, researchers used functional (fMRI) to look at the children’s brain activity after they took L-theanine, caffeine, a combination of the two, or a placebo over 4 days.

Compared with the placebo, L-theanine, caffeine, and the combination of the two improved concentration and thinking ability. The combination also decreased impulsivity, a common ADHD symptom.

A different 2019 study involving 30 healthy adults compared the benefits of 200 milligrams (mg) of L-theanine to a placebo over 30 days.

Verbal fluency and executive functioning improved in the L-theanine group relative to the placebo group, suggesting it could boost cognitive performance.

However, participants did not have ADHD, so it is unclear whether these benefits would extend to people with the condition.

The small size of these studies, however, means they are not conclusive. More research is necessary with larger and more varied participants.

Research on L-theanine has not been exhaustive. Researchers do not know all its potential side effects or drug interactions. Preliminary research suggests few side effects, but this research draws on very limited data.

In the previously mentioned 2019 study with healthy adults, all participants remained in the study, suggesting side effects were not severe. No one reported adverse effects.

In the 2019 study with children, 1 of 5 participants developed facial tics. These went away after stopping the L-theanine treatment.

L-theanine is not a medication that has been rigorously tested, so there is no standardized dose.

The 2019 study with children used a dose of 2.5 mg per kilogram of body weight, while the 2019 study with adults gave all participants 200 mg of L-theanine. These doses may be a good starting guideline, but a person should consult a doctor before trying it.

Alternatively, a person can get both L-theanine and caffeine, which may be more beneficial together, from green tea.

There is no evidence that L-theanine can replace ADHD treatment.

However, it may complement or supplement treatment. In people for whom ADHD treatment is unsafe or ineffective, it could be an alternative.

Research on L-theanine is new, and there is very little such research. Therefore, there is no basis for making claims about L-theanine as an ADHD treatment. People should be skeptical of anyone who tells them to stop taking their usual medication.

Some questions to ask a doctor include:

  • Are there any dietary or lifestyle changes I could make that would improve the effectiveness of my ADHD medication?
  • Is it safe to try L-theanine or tea with my current medication regimen?
  • Is L-theanine likely to interact with my medications?
  • What are the goals of treatment?

L-theanine, especially combined with caffeine, might be a potential ADHD treatment. Anecdotally, many people with ADHD report improvements in their symptoms when drinking green tea.

But it is not certain that L-theanine explains these improvements. Caffeine or another substance could be the reason for the improvement.

People who want to try alternative or complementary ADHD treatments need to consult a doctor knowledgeable about supplements.