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Acta Neuropsychiatr. 2015 Oct;27(5):291-6. doi: 10.1017/neu.2015.22. Epub 2015 Apr 21.

Effect of L-theanine on glutamatergic function in patients with schizophrenia.

Author information

1Department of Mental Disorder Research,National Institute of Neuroscience,National Center of Neurology and Psychiatry,Tokyo,Japan.
2Department of Radiology,National Center of Neurology and Psychiatry,Tokyo,Japan.
3Department of Research and Development,Nutrition Division,Taiyo Kagaku Co., Ltd,Mie,Japan.



Glutamatergic dysfunction in the brain has been implicated in the pathophysiology of schizophrenia. Previous studies suggested that L-theanine affects the glutamatergic neurotransmission and ameliorates symptoms in patients with schizophrenia. The aims of the present study were twofold: to examine the possible effects of L-theanine on symptoms in chronic schizophrenia patients and to evaluate the changes in chemical mediators, including glutamate + glutamine (Glx), in the brain by using 1H magnetic resonance spectroscopy (MRS).


The subjects were 17 patients with schizophrenia and 22 age- and sex-matched healthy subjects. L-theanine (250 mg/day) was added to the patients' ongoing antipsychotic treatment for 8 weeks. The outcome measures were the Positive and Negative Syndrome Scale (PANSS), Pittsburgh Sleep Quality Index scores and MRS results.


There were significant improvements in the PANSS positive scale and sleep quality after the L-theanine treatment. As for MRS, we found no significant differences in Glx levels before and after the 8 week L-theanine treatment. However, significant correlations were observed between baseline density of Glx and change in Glx density by l-theanine.


Our results suggest that L-theanine is effective in ameliorating positive symptoms and sleep quality in schizophrenia. The MRS findings suggest that L-theanine stabilises the glutamatergic concentration in the brain, which is a possible mechanism underlying the therapeutic effect.


glutamine+glutamate; l-theanine (N-ethyl-l-glutamine); magnetic resonance spectroscopy; schizophrenia

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