Can L-theanine (amino acid) be used to treat anxiety?

L-Theanine for Anxiety: Clinical Recommendation

L-theanine is not recommended as a primary treatment for anxiety disorders, as it lacks sufficient evidence for efficacy and is not included in any major clinical practice guidelines for anxiety management. 1

Guideline-Based First-Line Treatments

SSRIs and SNRIs are the established first-line pharmacological treatments for anxiety disorders, with cognitive-behavioral therapy (CBT) as the preferred initial approach, particularly for mild to moderate presentations. 1

• CBT should be considered the first-line treatment for anxiety in both adolescents and adults, with SSRIs as an alternative when quality CBT is unavailable or for more severe presentations. 1
• Combination treatment (CBT plus SSRI) demonstrates superior efficacy compared to either treatment alone for anxiety disorders. 1
• SSRIs have high treatment response rates (NNT = 4.70) with dropout rates similar to placebo, indicating both efficacy and safety. 1
• SNRIs show comparable efficacy to SSRIs (NNT = 4.94) with similar safety profiles. 1

L-Theanine: Evidence Summary

Perioperative Guideline Context Only

The only guideline mention of L-theanine (theanine) is in the perioperative setting, where it is recommended to hold for 24 hours before surgery due to dose-dependent blood pressure decreases and rapid metabolism. 1

• This perioperative recommendation does not constitute an endorsement for anxiety treatment. 1
• The guideline notes CNS depressive effects but only in the surgical context. 1

Research Evidence Limitations

The research evidence for L-theanine in anxiety is insufficient and contradictory:

• A 2019 double-blind RCT (n=46) found no benefit for L-theanine (450-900 mg) as adjunctive treatment in generalized anxiety disorder, with no separation from placebo on the Hamilton Anxiety Rating Scale (p=0.73). 2
• A 2004 study showed no anxiolytic effects during experimentally-induced anxiety states, with only minimal relaxing effects under baseline resting conditions. 3
• One positive study in schizophrenia patients showed anxiety reduction (p=0.015), but this population and context differ substantially from primary anxiety disorders. 4
• Narrative reviews suggest doses of 200-400 mg daily may have anxiolytic effects, but acknowledge the need for more rigorous randomized controlled trials before clinical recommendations can be made. 5

Clinical Algorithm for Anxiety Treatment

For patients presenting with anxiety disorders:

1. Initiate CBT as first-line treatment for mild to moderate anxiety presentations. 1
2. Consider SSRI monotherapy (sertraline, escitalopram, paroxetine, or fluvoxamine) for moderate to severe presentations or when CBT is unavailable. 1
3. Use combination CBT plus SSRI for optimal outcomes, particularly in severe cases. 1
4. Consider SNRIs (venlafaxine, duloxetine) as second-line pharmacotherapy if SSRIs are ineffective or not tolerated. 1
5. Monitor weekly for adverse effects during the first months of SSRI/SNRI treatment, particularly for increased anxiety, agitation, or suicidal ideation. 6

Critical Pitfalls

• Do not use L-theanine as a substitute for evidence-based treatments (CBT, SSRIs, SNRIs) in patients with diagnosed anxiety disorders. 1
• Do not delay initiation of proven therapies while attempting unproven supplements. 1
• The absence of L-theanine from all major anxiety treatment guidelines (AACAP, NCCN, WPSI, Japanese Society guidelines) reflects insufficient evidence for clinical use. 1
• Cases of hepatotoxicity have been reported with green tea extract consumption, warranting caution with L-theanine supplementation. 5