One of my mainstay nutraceuticals for general anxiety disorder is L-theanine, even though the research is not consistent or considerable. My clinical experience is what mostly guides my consistent recommendations for it.
Theanine is a non-protein amino acid that was first isolated from green tea and is chemically similar in structure to glutamic acid. L-theanine is the predominant isomer and is the subject of most of the research.
One randomized, placebo-controlled, crossover, and double-blind trial evaluated the effects of 200 mg/day L-theanine vs. placebo for 4 weeks in nine men and 21 women on stress-related symptoms and cognitive functions. [i] The Self-Rating Depression Scale, State-Trait Anxiety Inventory, and Pittsburgh Sleep Quality Index (PSQI) scores decreased after L-theanine administration. The PSQI subscale scores for sleep latency, sleep disturbance, and use of sleep medication reduced after L-theanine administration as well. In addition, cognitive functions, verbal fluency and executive function scores improved after L-theanine administration. Research reported that the findings suggest that L-theanine has the potential to promote mental health in the general population with stress-related ailments and cognitive impairments.
However, another small clinical study showed that taking a single dose of 200 mg L-theanine does not reduce experimentally induced anticipatory anxiety when compared with placebo. [ii]
It’s not clear if L-theanine improves depression but as we know, depression and anxiety often co-exist. There was a small clinical study demonstrating that 250 mg/day L-theanine at bedtime, for 8 weeks shows that taking a specific L-theanine product reduces mild depression and improves sleep quality compared to baseline.[iii] However, there was not a placebo or comparison group.
For an anticipated stressful event, one might think of L-theanine just prior. One very small clinical study shows that 200 mg prior to a stress-inducing exam reduces tension-anxiety when compared with placebo. [iv] Other clinical research implies that taking 200 mg twice daily for one week prior to and the first 10 days of a stressful period decreases subjective stress scores when compared with placebo.[v] While it seems to be able to induce a feeling of calm, it may not consistently be effective for anticipatory anxiety. [vi]
I have not found any clear information about overdose issues and studies have not exceeded 8 weeks. My usual recommendations are 100-200 mg one to twice daily. To my knowledge, I have not seen any consequences of overdosing, but my comfort zone has been a maximum of 200 mg, three times daily for ongoing use. I do think another use of it is as needed, or short-term use for anticipated or immediate stressful times. Another aspect that I like about using L-theanine, is I can easily use it daily along with other natural products or even medications for anxiety disorder.
References:
[i] Hidese S, Ogawa S, Ota M, et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: A randomized controlled trial. Nutrients. 2019;11(10).
[ii] Lu K, Gray MA, Oliver C, et al. The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans. Hum Psychopharmacol 2004;19:457-65.
[iii] Hidese S, Ota M, Wakabayashi C, et al. Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta Neuropsychiatr 2017;29(2):72-9.
[iv] Yoto A, Motoki M, Murao S, Yokogoshi H. Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. J Physiol Anthropol. 2012;31:28.
[v] Unno K, et al. Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary a-amylase activity, trait anxiety and subjective stress. Pharmacol Biochem Behav. 2013;111:128-135.
[vi] Lu K, Gray MA, Oliver C, et al. The acute effects of L-theanine in comparison with alprazolam on anticipatory anxiety in humans. Hum Psychopharmacol 2004;19:457-65.
