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L-Theanine for Insomnia: Does It Work?

by Dale Cudmore | Updated: Jan 02, 2023

L-Theanine is an amino acid from green tea. It’s known to increase levels of important neurotransmitters for sleep in the brain like GABA, serotonin, and dopamine (1). It’s likely one of the reasons that green tea can improve insomnia.

The l-theanine supplements that you can buy over the counter are typically synthesized to have much greater concentrations than you would find in tea.

Just how much of an effect does it have on sleep?

That’s what we’re going to find out after summarizing current research on the amino acid.

The Effect of L-Theanine on Stress and Sleep

A study with 30 subjects who were more or less healthy looked at the effects of daily l-theanine administration (200 mg per day) vs a placebo group (2).

After 4 weeks, they found significant improvements in depression, anxiety, and sleep quality scores.

A bigger sample size would have been nice, but the large effect size still led to statistically significant outcomes.

Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI), which is the most common test. You can use our PSQI online calculator if you’re curious about your own score.

The Effect of L-Theanine on Depression

Another study looked at how l-theanine impacted patients with major depressive disorder (3).

Patients had 250 mg of l-theanine added to their current medication for 8 weeks. Depression was measured using Hamilton Depression Rating Scale (HAMD-21), which decreased by approximately 30% in subjects with unremitted depression.

It did not have a significant effect in those with remitted symptoms.

SummaryL-theanine can be a safe addition to depression treatment plans.

Combining L-Theanine With Other Herbal Remedies May Improve Results

The nice thing about “natural” ingredients is that they’re usually safe as long as they’re not abused. Unlike other sleep medication, they don’t tend to have significant interactions with other medication that can be dangerous.

One research team looked at the effect of combining l-theanine with another popular over the counter sleep supplement - GABA (4). The subjects:

Summary...showed a decrease in sleep latency and an increase in sleep duration compared to GABA or theanine alone

It will be interesting to see if the effects of l-theanine can be improved by combining it with other natural sleep aids like melatonin.

Can Children Take L-Theanine?

Amino acids are naturally occurring, so it stands to reason that children could also take l-theanine with little risk as long as it’s taken as directed.

One study examined the effects of l-theanine on sleep quality in boys with ADHD (5).

Subjects had high sleep efficiency (percent of time spent asleep), and a non-significant trend for less activity during sleep (a larger sample size might confirm this effect).

It appears that the calming effects of l-theanine may apply to children as well, but more research is required.

Summary: L-Theanine and Sleep Quality

Compared to most natural sleep aids, there’s quite a bit of robust evidence that indicates that l-theanine can improve sleep quality.

It’s not going to cure insomnia by itself, but it may make a nice addition to a treatment plan, and there don’t appear to be any common adverse side effects.


  1. The Neuropharmacology of L-Theanine(N-Ethyl-L-Glutamine
  2. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial
  3. Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study
  4. GABA and l-theanine mixture decreases sleep latency and improves NREM sleep
  5. The Effects of L-Theanine (Suntheanine) on Objective Sleep Quality in Boys with Attention Deficit Hyperactivity Disorder

Medical Disclaimer: The information on is not intended to be a substitute for physician or other qualified care. We simply aim to inform people struggling with sleep issues about the nature of their condition and/or prescribed treatment.

About the authorDale is the founder of Snooze University and a sleep researcher. I overcame my sleep issues and now I'd like to help you do the same by summarizing the latest sleep studies for you.