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Review
. 2021 Dec 30;13(12):e20828.
doi: 10.7759/cureus.20828. eCollection 2021 Dec.

The Cognitive-Enhancing Outcomes of Caffeine and L-theanine: A Systematic Review

Anas Anas Sohail  1 , Fernando Ortiz  2 , Teresa Varghese  3 , Stephanie P Fabara  4 , Arshdeep S Batth  5 , Darshan P Sandesara  6 , Ahtesham Sabir  7 , Mahika Khurana  8 , Shae Datta  9 , Urvish K Patel  10
Affiliations
Review

The Cognitive-Enhancing Outcomes of Caffeine and L-theanine: A Systematic Review

Anas Anas Sohail et al. Cureus. .

Abstract

Attention-deficit hyperactivity disorder (ADHD) affects multiple cognitive domains, including impaired attention, hyperactivity, and increased impulsivity. According to the CDC, 9.4% of children between 2 and 17 years old have been diagnosed with ADHD. Neurotransmitters such as noradrenaline and dopamine have been suggested as crucial players in the pathophysiology of ADHD and are often targets of modern medication. Adenosine receptors types A1 and A2a in the brain are inhibited by caffeine: a stimulant known to augment attention by increasing cholinergic and dopaminergic transmission. The cognitive function of attention is also enhanced by the amino acid: L-theanine. The mechanism of action is that it behaves like a glutamate reuptake inhibitor while also acting in the hippocampus as a competitive low-affinity glutamate receptor antagonist. It's also shown to have a neuroprotective effect by its action on the gamma aminobutyric acid (GABA)-A receptors. Our systematic review investigates the literature and clinical trials on the cognitive-enhancing effects of caffeine and L-theanine.

Keywords: adhd; caffeine; green tea; l-theanine; l-theanine and caffeine; matcha; memory reconsolidation; mental cognition.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) flowchart
See this image and copyright information in PMC

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