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Integrative Psychiatry Supplement Spotlight: L-Theanine

L-theanine, green tea leaves

While it may seem straightforward, integrative or holistic psychiatry can actually cover a pretty large spectrum. On one end of the spectrum, are additional recommendations to help with someone's symptoms that are not pharmaceutical medications. On the other end of the spectrum is looking deeply for underlying causes of someone's symptoms - anything from infection, to mold, or biochemical imbalances.

There is an important role for both - and everything in between. (And a reminder to do your homework on your integrative/holistic psychiatrist or psychiatric nurse practitioner as to what spectrum they cover and have expertise in before you commit to working with them).

Today, I'll be sharing more from the symptomatic support spectrum and the utility of L-theanine for mental health. It is a commonly used supplement and I have even now seen it available in the pharmacy aisle at Walgreens while I wait for my passport photo.


What is L-Theanine?

L-theanine is an amino acid most often found in green and black tea leaves. It is also in the Bay Bolete mushroom but in the supplements you buy, it is typically sourced from green tea leaves. The tea leaves go through a process that includes water extraction, filtration, and purification. It is typically bought in capsule form - I have not seen other forms of it besides in its natural tea form. A cup of green tea will typically have around 20-37 mg of l-theanine and the doses used in the studies mentioned below are usually between 200-400 mg, for reference.


Underlying mechanisms

L-theanine is thought to promote relaxation and improve sleep quality by increasing the levels of GABA, an inhibitory neurotransmitter in the brain. GABA plays a key role in regulating sleep and mood, and its deficiency is also linked to some sleep disorders. Other substances that act on GABA include alcohol and benzodiazepines but L-theanine is not habit forming or have the same potential side effects as these. While the beverage of green tea has caffeine, L-theanine does not. It also is not going to sedate an individual like other anti-anxiety treatments that exist, like benzodiazepines do.


What does the research say about the use of L-Theanine for mental health?

Generalized Anxiety

There was a meta-analysis by Hidese et al. done in 2021 (1) that found that L-theanine supplementation significantly reduced anxiety symptoms compared to placebo. The results were consistent across different anxiety measures and study populations.

The dose used in the studies analyzed ranged from 50-400 mg daily, with the most common range between 200-400 mg. Some studies used a single daily dose, while others used multiple doses throughout the day. The duration of supplementation also varied across studies, ranging from 2 weeks to 3 months.

Obesessive Compulsive Disorder (OCD)

Only a few small-scale studies have investigated L-theanine for OCD, with mixed results. In one study from 2023 (2) found that when L-theanine was combined with the SSRI, fluvoxamine (also known as Luvox) in patients with moderate to severe OCD, the addition of L-Theanine significantly improved OCD symptoms compared to the placebo. The dose in this study was 200 mg twice a day.

There was another study from 2018 (3) that evaluated the effectiveness of a combination of supplements for OCD that included magnesium, P5P (the active form of Vitamin B6), selenium, and zinc. A modest improvement in OCD symptoms was found - and that the L-theanine effects couldn't be isolated.

Post Traumatic Stress Disorder

There have been limited studies looking at L-theanine as a possible treatment option for PTSD. It's hard to generalize from the studies since their participant sizes are so small. One small study (4) found that L-theanine was helpful for reducing anxiety that may be part of someone's symptoms of PTSD, which means it likely won't resolve flashbacks or reliving traumatic memories but may help with the anxiety associated with it. The dose used in this study was 200 mg daily.

What about for nightmares? This hasn't been studied. L-theanine can help sleep for some individuals; the scores for sleep latency, sleep disturbance, and use of sleep medication reduced after L-theanine administration, compared to the placebo administration in the study mentioned above.


There is growing evidence suggesting L-theanine may be beneficial for improving insomnia and sleep quality.

Reduced sleep latency (time it takes to fall asleep): Studies (4, 5) have shown L-theanine can shorten the time it takes to fall asleep, leading to quicker and easier sleep onset.

Increased sleep duration: L-theanine has been shown to increase total sleep duration, providing individuals with more restful sleep. It has also been shown to decrease cortisol levels (5), which can improve sleep.

Enhanced sleep stages: Research (4, 6) suggests L-theanine may increase the amount of deep sleep (slow-wave sleep), which is crucial for restoration and cognitive function.

Reduced daytime dysfunction: Individuals taking L-theanine have reported feeling less tired and more alert during the day, indicating improvements in daytime functioning (5.7).


Another interesting addition is that L-theanine may help with ADHD symptoms. L-theanine can increase alpha waves in the brain. Alpha waves are associated with a state of relaxed alertness and focused attention. Side note - other treatments that may improve ADHD symptoms that also increase alpha waves includes meditation, neurofeedback, yoga, and biurnal beats.

L-theanine's ability to promote alpha activity might help reduce mind wandering and improve the ability to stay focused on tasks. The research I point to most often is the "Effects of L-theanine on Attention and Reaction Time Response: A Systematic Review and Meta-Analysis", published in November 2022 in the journal, Nutrients. This review analyzed 12 randomized controlled trials to investigate the effects of L-theanine on attention and reaction time.

Key findings of the study found:

Improved attention performance: L-theanine supplementation significantly improved attention performance, as measured by various tests.

Especially helpul for ignoring distractions: The effect of L-theanine was more pronounced on attentional control tasks, such as those requiring inhibiting distractions or switching attention between tasks.

Improved reaction time: L-theanine also improved reaction time, suggesting faster information processing.

The optimal dosage for improving attention and reaction time appeared to be 200mg daily, with no additional benefits observed at higher doses.


What are the side effects?

Overall, L-theanine supplementation is considered safe and well-tolerated. While side effects are rare, they can occur and may include:

Stomach upset: This is the most common side effect reported, but it is generally mild and transient.

Headache: Some individuals may experience headaches after taking L-theanine, but this often subsides with continued use.

Drowsiness: L-theanine has a relaxing effect, which may lead to drowsiness (but not sedation) in some individuals, especially at higher doses.

Anxiety: In rare cases, L-theanine may exacerbate anxiety symptoms in individuals prone to anxiety.

It's important to consult your healthcare professional before taking L-theanine, especially if you are already taking any medications or supplements. They can help you assess potential interactions and determine if L-theanine is safe and appropriate for you.


What form of L-Theanine is best?

You might see "Suntheanine" on the supplement label. This is actually a patented form of L-theanine that is touted for its superior purity compared to the non-patented form of L-theanine.

So is it better? The jury is still out.

Direct comparative studies between Suntheanine and other forms of L-theanine have not been done. Most research doens't actually distinguish between Suntheanine and other forms of L-theanine, making it difficult to conclusively say that Suntheanine is superior. Suntheanine seems to have the same bioavailability and safety profile as L-theanine.

A kind reminder: This blog post is designed as a general guide. This is not a substitute for personalized medical advice, nor is a patient-physician relationship established in this blog post.

Become a patient: To start your integrative mental health journey at Driftless Integrative Psychiatry, we would be honored to help. Learn more here.


  1. L-theanine for anxiety: a systematic review and meta-analysis (2021) by Hidese et al. (PMID: 34781239)

  2. L-theanine combination therapy with fluvoxamine in moderate-to-severe obsessive-compulsive disorder: A placebo-controlled, double-blind, randomized trial (2023) by Han et al. (PMID: 37169515)

  3. Treatment of refractory obsessive-compulsive disorder with nutraceuticals (TRON): a 20-week, open-label pilot study (2018) by Bloch et al. (DOI: 10.1016/j.cnsspec.2018.07.016)

  4. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial by Hidese S, Ogawa S, Ota M, Ishida I, Yasukawa Z, Ozeki M, Kunugi H. . Nutrients. 2019 Oct 3;11(10):2362. doi: 10.3390/nu11102362. PMID: 31623400; PMCID: PMC6836118.

  5. L-Theanine dietary supplementation effects on stress-induced cortisol and alpha-amylase in humans: a randomized, double-blind, placebo-controlled trial by Sakurai K, Katsumata K, Suzuki K, Asai A, Uehara M, Sasaki K, Kimura K. . Nutr Res.

  6. Effects of L-theanine on the sleep of elderly volunteers monitored by EEG by Kakuda T, Unno K, Hori S, Onoda M, Hayashi Y. . Nutr Sci Vitaminol (Tokyo). 2003 Jun;49(3):167-72. doi: 10.3177/jnsv.49.167. PMID: 12878367.

  7. L-Theanine reduces psychological and physiological stress responses by Kimura K, Ozeki M, Juneja LR, Ohira H. Biol Psychol. 2007 Dec;74(1):39-45. doi: 10.1016/j.biopsycho.2006.06.001. PMID: 16930973.


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