L-theanine

L-theanine is marketed as a «natural sleep aid» in sleep formulas with melatonin, magnesium and valerian. Small RCTs in healthy students with pre-exam anxiety reported improved subjective sleep quality; no data in chronic insomnia. AASM 2021 and SES 2016 choose CBT-I as first-line for chronic insomnia; L-theanine is in no international sleep guideline. If L-theanine was recommended for chronic insomnia instead of CBT-I or workup for sleep apnoea and restless legs syndrome, consider seeking a second opinion.

L-theanine with caffeine is marketed as a «focus stack» (Mind Lab Pro, Alpha Brain and analogues) promising «better focus without jitter». Several small RCTs showed modest improvement in reaction time and attention accuracy with L-theanine 100-200 mg + caffeine 50-100 mg versus caffeine alone in healthy volunteers. The effect is short-lived and comparable to one cup of green tea (about 25-50 mg L-theanine and 30 mg caffeine). EFSA 2011 approved no cognitive claim for L-theanine. No data in ADHD, Alzheimer or vascular dementia. If L-theanine was recommended as a stimulant substitute for ADHD, consider seeking a second opinion.

L-theanine is the main marketing claim from supplement makers: promises to «relieve stress», «remove anxiety» and «relax without drowsiness». A 2019 Nutrients systematic review found 9 RCTs in 200-400 healthy volunteers: modest short-term effect on acute stress (public speaking, tests); no data on chronic anxiety. EFSA 2011 did not approve a health claim. NICE 2022 lists SSRIs, SNRIs and CBT for anxiety and depression – L-theanine is not mentioned. Same for SEP 2014. If L-theanine was recommended for panic attacks, GAD or social phobia instead of psychotherapy referral, consider seeking a second opinion.