Synopsis

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

L-Theanine is an amino acid commonly found in tea leaves, especially green tea, and is often used as a dietary supplement for its purported calming properties. Scientific interest in theanine centers on its potential to modulate neurotransmitter levels in the brain, such as GABA, serotonin, and dopamine, which are all involved in regulating mood. Several small-scale clinical trials and animal studies have suggested that theanine may reduce symptoms of anxiety and promote relaxation without sedation. For example, a 2019 double-blind, placebo-controlled study published in Journal of Psychiatric Research found that 8 weeks of theanine supplementation reduced symptoms of anxiety and improved sleep quality in individuals with generalized anxiety disorder. However, specific clinical evidence for theanine in the treatment or management of "mood swings"—as opposed to general anxiety or stress—remains limited. Most studies focus on anxiety or stress reduction rather than the rapid mood fluctuations characteristic of mood swing disorders (e.g., bipolar disorder). While some users report subjective improvements in mood stability, robust, large-scale clinical trials directly examining theanine’s effects on mood swings are lacking. Thus, while the use of theanine for mood swings has some scientific plausibility based on its anxiolytic and mood-modulating effects, the supporting evidence is preliminary and indirect.

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