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L-Theanine for Sleep-Related Cognitive Impairment

C Some Evidence Limited evidence from small studies, but some positive signals exist.

Research suggests L-theanine supports sleep quality without sedation and may improve next-day cognitive performance through enhanced sleep architecture.

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The Bottom Line

            
            
Research suggests L-theanine supports sleep quality without sedation and may improve next-day cognitive performance through enhanced sleep architecture.

            
            
        

    










    

  
Key Study Findings





    

        
        

            

                
                    Randomized Controlled Trial
                
                
                
                4.3 weeks
                
                
                Single-blind
                
            

            
                Assessing brain function in stressed healthy individuals following the use of a combination of green …
            
            

                
                Dose: None
                
                
                vs: placebo
                
                
                Outcome: Brain response to stress and quality of life
                
                
                Effect: None
                
                
                p = 0.001
                
            

            
            
Population: Chronically stressed but healthy subjects

            
        

        
        

            

                
                    Randomized Controlled Trial
                
                
                n=46
                
                
                10 weeks
                
                
                Double-blind
                
            

            
                L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial.
            
            

                
                Dose: 450-900 mg L-theanine daily
                
                
                vs: Placebo
                
                
                
                Effect: None
                
                
                p=0.73 (anxiety), p=0.35 (inso
                
            

            
        

        
        

            

                
                    Controlled Clinical Trial
                
                
                n=20
                
                
                8 weeks
                
                
                Open-label
                
            

            
                Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study.
            
            

                
                Dose: 250 mg/day
                
                
                vs: Placebo
                
                
                Outcome: HAMD-21 depression score, cognitive function
                
                
                Effect: None
                
                
                pp0.007
                
            

            
            
Population: Patients with major depressive disorder

            
        

        
    







    
    

        
        

            

  
Key Statistics





            


    

        
6

        
Studies

    

    

        
400

        
Participants

    

    

        
            
            ↑
            
        
        
Positive

    

    

        C

        
Grade

    




        


        
        
        

            

  
Referenced Papers





            

                
                

                    

                        
                            Assessing brain function in stressed healthy individuals following the use of a combination of green tea, Rhodiola, magnesium, and B …
                        
                        
                            
                                Other
                            
                            
                            
                        
                    

                    

                        Frontiers in nutrition
                        2023
                        
                        3 citations
                        
                    

                

                
                

                    

                        
                            L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial.
                        
                        
                            
                                RCT
                            
                            
                            
                        
                    

                    

                        Journal of psychiatric …
                        2019
                        
                        46 citations
                        
                    

                

                
                

                    

                        
                            Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study.
                        
                        
                            
                                Other
                            
                            
                            
                        
                    

                    

                        Acta neuropsychiatrica
                        2017
                        
                        84 citations
                        
                    

                

                
            

        

        

        
        
        

            

  
Dosage & Usage





            
mg = milligrams · mcg = micrograms (1,000× smaller) · IU = International Units


            
            

                
Commonly Used Dosages

                

                    
                    

                        
general:

                        
100-200 mg/day

                    

                    
                    

                        
withcaffeine:

                        
200 mg L-theanine + 100 mg caffeine

                    

                    
                

                
                

                    Upper limit: 900 mg/day (no adverse effects observed in studies)
                

                
            

            

            
            

                
Dosages Studied in Research

                

                    

                        
                            

                                Dosage
                                Duration
                                Effect
                                N
                            

                        
                        
                            
                            

                                None
                                4.3 weeks
                                
                                    
                                    Positive
                                    
                                
                                --
                            

                            
                            

                                450-900 mg L-theanine daily
                                10 weeks
                                
                                    
                                    Neutral
                                    
                                
                                46
                            

                            
                            

                                250 mg/day
                                8 weeks
                                
                                    
                                    Positive
                                    
                                
                                20
                            

                            
                        
                    

                

            

            

            
            

                Best taken: Morning or as needed; rapid onset (30-60 minutes)
            

            
        

        

        
        
        

            

  
Safety & Side Effects





            

                
                

                    
Reported Side Effects

                    
    
                        
                        
  • 
                            ⚠
                            Generally very well-tolerated
                        
    • 
                        
                        
  • 
                            ⚠
                            Mild drowsiness in sensitive individuals
                        
    • 
                        
                        
  • 
                            ⚠
                            Mild headache (rare)
                        
    • 
                        
                    

                

                

                
                

                    
Known Interactions

                    
    
                        
                        
  • 
                            ●
                            Antihypertensive drugs (may enhance blood pressure lowering)
                        
    • 
                        
                        
  • 
                            ●
                            Stimulant medications (counteracts some stimulant side effects)
                        
    • 
                        
                        
  • 
                            ●
                            Sedative medications (additive calming effects)
                        
    • 
                        
                    

                

                

                
                

                    

                        Tolerable upper intake: 900 mg/day (no adverse effects observed in studies)
                    

                

                
            

            

                Always consult your healthcare provider before starting any supplement.
            

        

        

        
        
        

            

  
Frequently Asked Questions





            




    
    

        
            Does L-Theanine help with Sleep-Related Cognitive Impairment?
            
        
        

            Based on 6 studies with 400 participants, there is limited but promising evidence that L-Theanine may support Sleep-Related Cognitive Impairment management. Our evidence grade is C (Some Evidence).
        

    

    
    

        
            How much L-Theanine should I take for Sleep-Related Cognitive Impairment?
            
        
        

            Studies have used various dosages. A commonly studied range is 100-200 mg/day. Always consult your healthcare provider before starting any supplement regimen.
        

    

    
    

        
            Are there side effects of L-Theanine?
            
        
        

            Reported side effects may include Generally very well-tolerated, Mild drowsiness in sensitive individuals, Mild headache (rare). Most side effects are mild and dose-dependent. Consult your doctor if you experience any adverse reactions.
        

    

    
    

        
            How strong is the evidence for L-Theanine and Sleep-Related Cognitive Impairment?
            
        
        

            We rate the evidence as Grade C (Some Evidence). This rating is based on 6 peer-reviewed studies with 400 total participants. The overall direction of effect is positive.
        

    

    




        

        

        
        
        

            

  




            

                
                

                    
Other ingredients for Sleep-Related Cognitive Impairment

                    

                        
                        
                            Melatonin
                            C

                        
                        
                        
                            Ashwagandha
                            C

                        
                        
                        
                            Magnesium L-Threonate
                            C

                        
                        
                        
                            Creatine
                            C

                        
                        
                    

                

                

                
                
                
            

        

        

    


    
    






  
References

  
    
    
    
  1. 
      [1]
      Gisèle Pickering et al..
      Front Nutr.
      2023.
      Assessing brain function in stressed healthy individuals following the use of a combination of green tea, Rhodiola, magnesium, and B …
      doi:10.3389/fnut.2023.1211321
      PubMed
    
    2. 
    
    
  2. 
      [2]
      Jerome Sarris et al..
      J Psychiatr Res.
      2019.
      L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial.
      doi:10.1016/j.jpsychires.2018.12.014
      PubMed
    
    3. 
    
    
  3. 
      [3]
      Shinsuke Hidese et al..
      Acta Neuropsychiatr.
      2017.
      Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study.
      doi:10.1017/neu.2016.33
      PubMed
    
    4. 
    
  















    

        FDA Disclaimer:
        These statements have not been evaluated by the Food and Drug Administration. The products and information on this website are not intended to diagnose, treat, cure, or prevent any disease. The evidence grades presented are based on our analysis of published peer-reviewed research and do not constitute medical advice. Always consult your healthcare provider before starting any supplement regimen.