Exploring The Impact Of L-Theanine On Anxiety And Wellness

Medically reviewed by Andrea Brant, LMHC
Updated June 19, 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 from supplements or green tea consumption and its potential health benefits.

Remember that while eating nutrient-dense foods may help reduce symptoms of certain mental health disorders, food and supplements are generally not recommended as replacements for professional mental health care. It’s also important to note that you should consult with your doctor and/or a qualified nutritionist about health promotion before making significant changes to your eating patterns or taking supplements.

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L-theanine: An amino acid found in green tea

L-theanine is an amino acid that’s a natural constituent part of certain teas—such as green, black, and oolong—and some types of mushrooms. Supplements for L-theanine besides oolong, green, and black tea are also available in the form of powders, capsules, and liquids. This amino acid and its chemical constituents have been used by people of various cultures for centuries to reduce anxiety and promote relaxation, and it also increases subjective alertness in some cases. In addition, a recent prospective, double-blind, randomized trial suggests that it may improve attention, memory, other cognitive functions, and executive brain function due to its neuroprotective effects. 

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 control—in the brain. It may also block L-glutamic acid from reaching glutamate receptors 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 may significantly reduce stress levels and decrease high blood pressure associated with stress in eight weeks or less with no known adverse side effects. 

The relationship between L-theanine and anxiety

Because L-theanine seems to help balance levels of various neurotransmitters related to stress, it may have positive effects on common symptoms of anxiety disorders and stress-related symptoms 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. One placebo-controlled clinical trial conducted in 2021 suggests that L-theanine may 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 in this placebo-controlled study also note that L-theanine consumption was “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 help reduce symptoms of other conditions as well—including attention-deficit/hyperactivity disorder (ADHD). This form of neurodivergence 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—which looked at both single-blind placebo-controlled and double-blind placebo-controlled trials—indicates that the combination of L-theanine and caffeine intake in particular may result in improvements in “short-term sustained attention and overall cognition,” with others suggesting that it could help with memory impairment as well. 

Similarly, a 2019 clinical trial found that L-theanine, caffeine content, and/or the two in combination seem to improve sustained attention tasks 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 L-theanine as a supplement.

Other potential benefits of amino acids like L-theanine

This substance found in green and black tea 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 improve their objective sleep quality—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. Finally, some research points to the potential of L-theanine and other amino acids given via perioperative oral administration to reduce stress and aid in recovery after surgery.

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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 eating patterns. 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 should be used with caution. 

It’s also worth noting that while the safety and potential short-term benefits of L-theanine and other tea constituents have been well-documented, there’s a lack of research on the potential long-term side 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

The potential effects of L-theanine do not make it a comprehensive treatment for clinical anxiety disorders or other mental health disorders. Like other lifestyle changes—such as eating nutritious foods and exercising regularly—it simply has the potential to help reduce symptoms as an adjunctive treatment 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 of CBT 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 from randomized controlled trials 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 and that promotes alert relaxation. Research suggests that it may also 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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