Exploring The Impact Of L-Theanine On Anxiety And Wellness

Medically reviewed by Andrea Brant
Updated February 23, 2024by BetterHelp Editorial Team

L-theanine—sometimes referred to as simply “theanine”—is a naturally occurring amino acid found in certain foods. Research as well as a long history of use across cultures suggests that this substance can have calming effects, which may be beneficial for those experiencing anxiety. Read on to learn more about L-theanine and its potential positive effects. 

Remember that while a healthy diet can help reduce symptoms of some mental health disorders in some cases, foods and supplements are generally not recommended as a replacement for professional mental health care. It’s also important to note that you should consult with your doctor and/or a qualified nutritionist before making changes to your diet or taking supplements.

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What is L-theanine?

L-theanine is an amino acid that can be found in certain teas, such as green, black, and oolong, and in some types of mushrooms. Supplements for L-theanine are also available in the form of powders, capsules, and liquids. It’s been used by people of various cultures for centuries to reduce anxiety and promote relaxation, and recent research suggests that it can also improve attention, memory, and other aspects of cognitive and executive function. 

Although researchers aren’t sure exactly how L-theanine works in the body, it’s widely believed that it increases serotonin and levels of GABA—a neurotransmitter that plays a role in nervous system regulation—in the brain. The combined effect is the relaxation of the nervous system and a reduction in stress hormones like cortisol. Studies suggest that consuming 200 mg of L-theanine daily can help reduce stress levels significantly within eight weeks or less with no known adverse side effects. Again, it’s important to speak to your doctor before beginning any new vitamin or supplement regimen.

The relationship between L-theanine and anxiety

Because L-theanine seems to help balance levels of various neurotransmitters related to stress, it can have positive effects on common symptoms of anxiety, such as:

  • Excessive worry and rumination
  • Restlessness
  • Irritability
  • Muscle tension

Researchers have examined this relationship in an attempt to learn more about how natural substances like this may benefit those experiencing mental health disorders like anxiety. One placebo-controlled trial conducted in 2021 suggests that L-theanine can help reduce anxiety symptoms. It notes that the supplement “significantly increased frontal region alpha power compared to placebo in response to an acute stress challenge”, changes that are “indicative of relaxation in the brain and suggest a calming response.” The researchers also note that the supplement was found to be “safe and well-tolerated by participants.” 

Getty/Daniel Allan

The relationship between L-theanine and ADHD

Because of its effects on neurotransmitter levels, L-theanine may also help reduce symptoms of other conditions as well—including attention-deficit/hyperactivity disorder (ADHD). This disorder is estimated to affect 4.4% of adults and is characterized by difficulty focusing, impulsive behavior, and/or over-activity. 

Research may support the potential link between L-theanine and reduced ADHD symptoms. A 2021 review of studies on the topic, for example, indicates that the combination of L-theanine and caffeine in particular may result in improvements in “short-term sustained attention and overall cognition”. Similarly, a 2019 study found that L-theanine, caffeine, and/or the two in combination “seem to improve sustained attention and overall cognitive performance” in children with ADHD by decreasing mind wandering. Note, however, that L-theanine may lessen the effectiveness of certain stimulant medications often prescribed for ADHD, so ask your doctor before taking it.

Other potential benefits of L-theanine

This substance may also have other positive health effects. Because it’s thought to increase dopamine levels in the brain, it can help support positive mood—which is why it’s being explored as potentially beneficial for those experiencing major depressive disorder. It may also help promote a state of relaxation in the brain that makes it easier for people to get quality sleep—which has links to a variety of physical and mental health benefits. Plus, sleep disturbances are frequently associated with both depression and anxiety, so L-theanine may help mitigate symptoms in this way as well.

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Is L-theanine safe?

Again, it’s recommended that you consult with a licensed healthcare provider before taking any kind of supplement or significantly altering your diet. One reason is that some supplements can cause negative interactions with certain medications. A medical professional can also help you determine an appropriate dose if they decide that this supplement is safe for you to take. Consuming too much L-theanine can lead to headaches, nausea, and other side effects. 

It’s also worth noting that while the safety and potential short-term benefits of L-theanine have been well-documented, there’s a lack of research on the potential long-term effects of consistently taking this supplement. It’s another reason why you should consult with your doctor before beginning any supplement use, especially if it’s over the long term.

Other treatments for anxiety

To reiterate, L-theanine is not considered to be a comprehensive treatment for clinical anxiety disorders or other mental health disorders. Like other lifestyle changes—such as eating a healthy diet and exercising regularly—it simply has the potential to help reduce symptoms and/or enhance the effects of professional treatment. 

Treatment for anxiety typically consists of some form of psychotherapy, sometimes in combination with medication. Cognitive behavioral therapy (CBT) in particular is one of the most common forms of talk therapy for people with anxiety disorders. The aim is to help an individual learn to recognize and shift distorted thought patterns that may be contributing to distress and other symptoms. A therapist can also help a person learn healthy coping mechanisms that can assist them in managing symptoms as they arise.

For some people with anxiety, the thought of meeting with a healthcare provider in person may seem intimidating and could even cause a spike in symptoms. Research suggests that online therapy can result in “sustained, clinically meaningful improvements” in anxiety symptoms just as in-person therapy can, so those who prefer this method may feel empowered to choose it. If you’re interested in trying online therapy, you might consider a platform like BetterHelp. You can get matched with a licensed therapist who you can meet with via phone, video call, and/or in-app messaging to address the challenges you may be facing—and all from the comfort of home or anywhere you have an internet connection. Whatever method you may choose, effective, compassionate support for anxiety symptoms is available. 


L-theanine is a naturally occurring amino acid that’s found in certain types of tea and some mushrooms. Research suggests that it may have calming and mood-boosting effects, making it a supplement that some individuals with anxiety disorders may want to speak to their doctors about.

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