Generalized anxiety disorder (GAD) is a common condition that affects 3.1% of the US population.¹ Up to one in five adults² (20%) suffer from an anxiety disorder.
Women are more likely³ than men to be affected by anxiety. One study⁴ found that the chances of developing any type of anxiety disorder over a lifetime were 30.5% for women and 19.2% for men.
A report⁵ by the World Health Organization (WHO) in 2017 found that anxiety was the sixth most common disorder causing significant disability in people’s lives in highly developed countries.
The mainstay of treatment for anxiety disorders is medication, usually selective serotonin reuptake inhibitors (SSRIs) or serotonin noradrenaline reuptake inhibitors, in conjunction with psychotherapy, such as cognitive behavior therapy.
There can be various reasons you may not want to take conventional medication for your anxiety. Perhaps you experience side effects with SSRIs or perhaps you just prefer not to take traditional medication. If this is the case, you might be looking for a more natural treatment for your anxiety.
There is some evidence⁶ that L-theanine may work to treat anxiety. If you are thinking of taking it to control your anxiety, you may want to know a bit more about it. Read on to discover what L-theanine is and whether there is any scientific backing for its use in the treatment of anxiety disorders.
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It’s normal to occasionally feel anxious, but when your anxiety symptoms start to interfere with your daily functioning, you may have an anxiety disorder. Some symptoms that you may experience if you have an anxiety disorder are:
Frequently feeling nervous, irritable, or on-edge
Feeling a sense of impending doom or danger
Having difficulty concentrating or focusing
If you struggle with an anxiety disorder, you may find that you experience excessive and persistent worry or fear about everyday situations, or you may have repeated episodes of intense fear and anxiety (commonly called panic attacks) that may be so severe it can feel as though you are having a heart attack.
You may find that you start adapting your lifestyle to avoid situations or activities that trigger your anxiety. When you have panic attacks that are so severe that you become too scared to leave the house, this may be known as panic disorder with agoraphobia.
According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V),² to be diagnosed with an anxiety disorder, your symptoms must have been present for at least six months, must result in significant distress or impairment in social and occupational areas and must not be attributable to a physical cause, such as an overactive thyroid.
Symptoms of an anxiety disorder often start in childhood or adolescence and continue into adulthood.
The exact cause of anxiety is not fully known. It is likely that anxiety disorders are caused by a combination of factors, including both your genes and your environment.
Genetics are known to play a role in the development of anxiety disorders. You are more likely to develop an anxiety disorder if you have a blood relative who suffers from an anxiety disorder.
There is evidence to suggest that an imbalance in your neurotransmitters may play a role in the development of anxiety disorders. People with low serotonin activity and elevated noradrenergic system activity may be more prone to developing anxiety.
The following factors have been identified as putting you more at risk of developing an anxiety disorder:
Stress as a result of ill health
Excessive or persistent life stressors
Personality type, as some personality types may be more prone to developing anxiety disorders
Other mental health disorders such as depression or substance abuse
Drug or alcohol use or misuse
L-theanine⁶ is a non-protein amino acid that is found in green and black tea (Camellia sinensis); this form of theanine⁸ is known as L-isomer. It is also found in some mushroom species (Xerocomus Badius), but is otherwise rare in nature. It can also be produced synthetically.
L-theanine is the most prevalent amino acid in tea leaves and is thought to contribute to the flavor of tea leaves. It makes up between 1% and 2% of the dry weight of tea, which translates to anything between 20mg to 60mg of L-theanine per 200ml of tea.
This is significant since tea is the second-most⁹ consumed beverage worldwide after water.
The structure of L-theanine resembles the structure of L-glutamic acid. It is thought that its mechanism of action may be via its attachment to glutamate receptors. Glutamate is one of the most important neurotransmitters in the brain. By mimicking glutamate, L-theanine¹⁰ can interact with the receptors usually activated by glutamate.
It is thought that this activity may influence serotonin secretion in specific areas of the brain.
L-theanine is able to cross the blood-brain barrier in mammals, which is how it is able to exert its effects on neurons in the brain. L-theanine starts having an effect on the brain within 30 minutes⁸ and can last in the bloodstream for a few hours.
L-theanine has been shown to help generate alpha waves in the brain. Brain waves⁹ are electrical impulses on the brain’s surface that are measured by electroencephalogram (EEG). Electrodes are attached to the scalp, which then measure the electrical impulses on the surface of the brain.
There are four different types of brain wave that indicate different states of brain activity: alpha waves are indicative of a relaxed, yet alert, state.
It is also likely that L-theanine regulates physiological functions, such as heart rate and blood pressure, which are increased during stressful events. This would potentially further contribute to the amino acid’s stress-reducing effects.
L-theanine has been shown¹⁰ to exert a calming effect and help control anxiety in laboratory animals, dogs, and cats, but is there evidence that it has an effect on anxiety in humans?
A 2019 study⁶ looked at the effect of 200mg L-theanine per day on 30 individuals, compared to a placebo. Stress-related symptoms were measured before and after four weeks of L-theanine treatment.
There was a significantly greater reduction in stress-related symptoms and sleep quality problems in the groups of participants receiving L-theanine than with the placebo.
A 2013 study¹¹ also looked at the effects of 200mg twice daily versus placebo in 20 pharmacy students undergoing a stint in a stressful pharmacy practice. Salivary amylase activity (SAA) was measured as a marker of stress and students were asked to self-evaluate their stress levels.
Both SAA and subjective anxiety scores were lower in the L-theanine group than the placebo group.
Another study,⁸ done in 2008, enrolled 35 participants to assess the effect of L-theanine on brain waves versus placebo. Participants were randomized to receive either 50mg of L-theanine or a placebo and their brain waves were measured for a period afterwards.
The participants receiving the L-theanine showed a greater increase in alpha brain-wave activity than those receiving the placebo.
Although these studies suggest that L-theanine may be beneficial in the treatment of anxiety, the study sample sizes are small and the doses of L-theanine were not standardized. At most, these studies suggest that it is worth investing through further studies so that the exact role of L-theanine in the management of anxiety can be defined.
L-theanine has been classified as “generally recognized as safe” by the FDA. It is sold in the United States as a dietary supplement. There are no unknown drug interactions or contraindications and few adverse events have been reported. Potential side effects from studies involving tea extracts include dizziness, headaches, and gastrointestinal symptoms.
L-theanine is an amino acid prevalent in tea leaves. It has a similar structure to glutamate and exerts its effects on the brain by binding to glutamate receptors. It is thought that it modulates serotonin levels through this action.
Several small studies have shown that L-theanine decreases stress scores in subjects taking it versus those taking a placebo. Further large, well-designed studies need to be done to confirm the findings. L-theanine is generally considered safe to take and is classified as a dietary supplement in the U.S.
Generalized anxiety disorder (GAD) | Anxiety & Depression Association of America
Generalized anxiety disorder (2022)