Effects of chronic<scp>l</scp>-theanine administration in patients with major depressive disorder: an open-label study

<jats:sec id="S0924270816000338_abs1" sec-type="general"><jats:title>Objective</jats:title><jats:p><jats:sc>l</jats:sc>-theanine, an amino acid uniquely contained in green tea (<jats:italic>Camellia sinensis</jats:italic>), has been suggested to have various psychotropic effects. This study aimed to examine whether<jats:sc>l</jats:sc>-theanine is effective for patients with major depressive disorder (MDD) in an open-label clinical trial.</jats:p></jats:sec><jats:sec id="S0924270816000338_abs2" sec-type="methods"><jats:title>Methods</jats:title><jats:p>Subjects were 20 patients with MDD (four males; mean age: 41.0±14.1 years, 16 females; 42.9±12.0 years).<jats:sc>l</jats:sc>-theanine (250 mg/day) was added to the current medication of each participant for 8 weeks. Symptoms and cognitive functions were assessed at baseline, 4, and 8 weeks after<jats:sc>l</jats:sc>-theanine administration by the 21-item version of the Hamilton Depression Rating Scale (HAMD-21), State-Trait Anxiety Inventory (STAI), Pittsburgh Sleep Quality Index (PSQI), Stroop test, and Brief Assessment of Cognition in Schizophrenia (BACS).</jats:p></jats:sec><jats:sec id="S0924270816000338_abs3" sec-type="results"><jats:title>Results</jats:title><jats:p>HAMD-21 score was reduced after<jats:sc>l</jats:sc>-theanine administration (<jats:italic>p</jats:italic>=0.007). This reduction was observed in unremitted patients (HAMD-21>7;<jats:italic>p</jats:italic>=0.004) at baseline. Anxiety-trait scores decreased after<jats:sc>l</jats:sc>-theanine administration (<jats:italic>p</jats:italic>=0.012) in the STAI test. PSQI scores also decreased after<jats:sc>l</jats:sc>-theanine administration (<jats:italic>p</jats:italic>=0.030) in the unremitted patients at baseline. Regarding cognitive functions, response latency (<jats:italic>p</jats:italic>=0.001) and error rate (<jats:italic>p</jats:italic>=0.036) decreased in the Stroop test, and verbal memory (<jats:italic>p</jats:italic>=0.005) and executive function (<jats:italic>p</jats:italic>=0.016) were enhanced in the BACS test after<jats:sc>l</jats:sc>-theanine administration.</jats:p></jats:sec><jats:sec id="S0924270816000338_abs4" sec-type="conclusion"><jats:title>Conclusion</jats:title><jats:p>Our study suggests that chronic (8-week)<jats:sc>l</jats:sc>-theanine administration is safe and has multiple beneficial effects on depressive symptoms, anxiety, sleep disturbance and cognitive impairments in patients with MDD. However, since this is an open-label study, placebo-controlled studies are required to consolidate the effects.</jats:p></jats:sec>