Primary Research · 2017
Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study
Hidese S, Ogawa S, Ota M, et al. · Acta Neuropsychiatrica, 2017
Key finding
8-week open-label study in major depressive disorder (n=20) found 250mg/day L-theanine improved depression, anxiety, sleep, and cognitive function scores — supporting adjunctive use alongside standard treatment.
Abstract
PubMed · PMID 27396868 →OBJECTIVE: l-theanine, an amino acid uniquely contained in green tea (Camellia sinensis), has been suggested to have various psychotropic effects. This study aimed to examine whether l-theanine is effective for patients with major depressive disorder (MDD) in an open-label clinical trial. METHODS: Subjects were 20 patients with MDD (four males; mean age: 41.0±14.1 years, 16 females; 42.9±12.0 years). l-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 l-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). RESULTS: HAMD-21 score was reduced after l-theanine administration (p=0.007). This reduction was observed in unremitted patients (HAMD-21>7; p=0.004) at baseline. Anxiety-trait scores decreased after l-theanine administration (p=0.012) in the STAI test. PSQI scores also decreased after l-theanine administration (p=0.030) in the unremitted patients at baseline. Regarding cognitive functions, response latency (p=0.001) and error rate (p=0.036) decreased in the Stroop test, and verbal memory (p=0.005) and executive function (p=0.016) were enhanced in the BACS test after l-theanine administration. CONCLUSION: Our study suggests that chronic (8-week) l-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.
Abstract sourced from PubMed, a database of the U.S. National Library of Medicine. Displayed in the authors’ own words for context; our critique is in the sections below.
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L-Theanine
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The same questions worth asking about any research paper, not just this one. Worth a minute even if you trust the grade.
Who was studied, and do you resemble them?
Supplement effects often depend on baseline status. Vitamin D helps people who are deficient; iron helps people who are anemic. A result in people unlike you may not apply to you.
What was measured, and does it matter in daily life?
A study that shows a blood marker moved isn't the same as a study that shows people felt or functioned better. Ask what the outcome means in practice.
How large was the effect — not just whether it was significant.
'Statistically significant' only means the effect is unlikely to be zero. It doesn't tell you the effect is large enough to notice. Look for effect sizes, not just p-values.
Who paid for the trial, and what did they stand to gain?
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Has anyone else replicated this?
Single positive trials are hypotheses. Replication by independent groups is what turns a hypothesis into reliable evidence. If the only positive trial is the one you're reading, wait.
Does the dose in the trial match what's being sold?
Supplement marketing routinely cites trials that used 5–10× the dose in the product. If the effective dose was 2 g/day and the capsule has 200 mg, expect roughly no effect.
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