Evidence supporting the use of: L-theanine
For the health condition: Bipolar Mood Disorder

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Synopsis

Source of validity: Scientific
Rating (out of 5): 2

L-theanine is a naturally occurring amino acid found primarily in green tea. Its use in supporting mood disorders, including Bipolar Mood Disorder, is primarily based on its anxiolytic (anxiety-reducing) and potential mood-stabilizing effects observed in some studies. There is emerging scientific interest in L-theanine for psychiatric conditions, as it is known to modulate neurotransmitters such as dopamine, serotonin, and GABA, all of which play roles in mood regulation. A handful of small clinical studies and case reports have explored L-theanine’s effects in patients with mood disorders, though most research has focused on anxiety and depression rather than bipolar disorder specifically.

One open-label study (Hidese et al., 2017) found that adjunctive L-theanine (250 mg/day) improved symptoms of anxiety and sleep disturbances in patients with major depressive disorder and bipolar disorder, suggesting potential benefit. Additionally, preclinical studies indicate that L-theanine may have neuroprotective effects and could influence glutamatergic signaling, which is implicated in the pathophysiology of bipolar disorder.

However, the overall evidence base is limited, with few high-quality randomized controlled trials specifically targeting bipolar disorder. Most clinical guidelines do not currently recommend L-theanine as a standard treatment for bipolar disorder, and it should not be used as a replacement for established therapies. In summary, while there is some preliminary scientific evidence supporting L-theanine’s use for mood stabilization, the quality and quantity of evidence are currently modest.

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