Recent evidence suggests that greater green tea consumption is associated with a reduced risk of psychiatric diseases such as depressive disorder. Theanine (L-theanine or L-γ-glutamylethylamide) , an amino acid uniquely contained in green tea, is known as a relaxing agent which has a chemical structure similar to glutamate. In our animal experiments, theanine improved sensorimotor gating as assessed with prepulse inhibition [PPI] and showed an antidepressant-like effect such as shortening the immobility time in the forced swimming test and upregulation of brain derived neurotrophic factor in the hippocampus. We found that single administration of theanine (200 or 400 mg) increased PPI in healthy individuals. Administration of theanine for 8 weeks mitigated positive symptoms and sleep quality in chronic schizophrenia patients. In an 8-week open-label study on major depressive disorder, theanine improved depressed mood, anxiety, sleep and cognitive function. These findings suggest that theanine has various psychotropic effects and is useful in the treatment of psychiatric disorders including schizophrenia and depressive disorder.

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Omega-3 polyunsaturated fatty acids (omega-3 PUFAs) are one of the most studied interventions among nutritional psychiatry. In this paper, we review the evidence for the efficacy of omega-3 fatty acids against psychiatric disorders. A number of meta-analyses of randomized controlled trials (RCTs) support the positive effects of omega-3 PUFAs supplementation in treating depression and reducing depressive symptoms. The latest evidence supports the efficacy of omega-3 PUFAs containing a high ratio of eicosapentaenoic acid (EPA) against depression. But the amount of omega-3 PUFAs and intervention period were diverse among previous RCTs. Moreover, the appropriate amount of supplemental omega-3 PUFAs may be different among countries because of differences among countries in the consumption of fish, but there are few available evidence in Japan. Apart from depression, there are not so many RCTs showing the efficacy of omega-3 PUFAs against psychiatric disorders. We introduced our RCTs aiming to attenuate posttraumatic stress symptom, and a well-known RCT aiming to reduce the rate of progression to first-episode psychosis in adolescents and young adults with subthreshold psychosis. Nutritional approaches are applicable to various populations including pregnant women and children in light of its safety. Further studies may achieve the practical use of nutritional approaches in prevention and treatment of psychiatric disorders.

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Accumulating evidence suggests that oxidative stress and inflammation play a role in the pathophysiology of psychiatric disorders such as schizophrenia and depression. Blood levels of pro-inflammatory cytokines in patients with schizophrenia or depression were significantly higher than those of healthy controls. Together, antioxidants and anti-inflammatory compounds have been suggested as the novel therapeutic drugs for schizophrenia and depression. Here the author would like to discuss the possibility of sulforaphane as prophylactic compound for schizophrenia and depression.

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The lack of clinical laboratory tests is a major obstacle in the reliable diagnosis and quantitative treatment assessment and prevention of psychiatric disorders and in the development of patient-centered psychiatric practices. Optical topography was approved as an Advanced Medical Technology in 2009, and has been approved as an insurance-covered auxiliary laboratory test for differential diagnosis of depressive state by Ministry of Health, Labour and Welfare in Japan since 2014. Near-infrared spectroscopy (NIRS) , theoretical basis of optical topography, is one of functional neuroimaging techniques that has been increasingly employed in psychology and psychiatry. NIRS examination of major depressive disorder, bipolar disorder, and schizophrenia using a verbal fluency task of only three minutes demonstrated diagnosis-specific characteristics of frontal lobe function. These characteristics have been established as suggesting potential diagnosis of bipolar disorder or schizophrenia in clinically diagnosed major depressive disorder. Two-thirds of the original articles on NIRS application in psychiatry have been published by Japanese researchers. In order to establish the application of NIRS as clinically useful laboratory tests in psychiatry, auxiliary nature of NIRS examination for differential diagnosis should be properly recognized both by patients and psychiatrists.

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Accumulating evidence shows that patients with schizophrenia have reduced cortical volume in several regions including anterior cingulate, medial and inferior prefrontal regions, temporal lobe, hippocampus, amygdala, thalamus and insula. Various researchers have made efforts to discriminate schizophrenia from controls using structural magnetic resonance imaging (MRI) . In early days researchers performed manual tracing of regions of interest and multivariate discrimination analysis. Recent mainstream is to use automated preprocessing such as voxel-based morphometry or cortical thickness analysis and extract features with machine learning technique. Many achieve 70~90% of accuracy, but clinical application is still on the way. Establishing a simple way for preprocessing, minimizing the difference across MRI scanners, and finding the optimal combination with some other tests are necessary for the breakthrough of clinical application.

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Despite growing knowledge of the pathologies of mental illnesses, disease-specific biomarkers or behavioral indicators with sufficient sensitivities for the differential diagnosis have not been established. The eye movements are sensorimotor functions that reflect information processing carried out in the brain, and abnormalities in eye movements are often observed in patients with mental illnesses. The patients with schizophrenia show difficulties in executing of the anti-saccade task, abnormalities in ocular tracking of moving target, abnormal exploratory eye movements when they freely viewed pictures or figures. These eye movement abnormalities are thought to be effective in distinguishing individuals with schizophrenia from healthy controls. We have worked on development of an integrated eye movement score that objectively represents normal to abnormal eye movements that can be used to help the diagnosis of schizophrenia. The present issue reviews the eye movement abnormalities in schizophrenia, the uses of them in diagnosis and our attempts in development of an integrated eye movement rating scale that indicates the degree of eye movement abnormality involving our future prospects.

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Diagnosis of mental illness has been made by a physician examining the symptoms, however, objective diagnosis method has not yet been established yet. It is necessary to examine a sufficient period of time to obtain information on symptoms and course necessary for diagnosis. Because there are difficulties in obtaining the required information in limited consultation hours in clinical practice, there is a need to develop objective and scientific diagnosis. In this paper, history of mental illness diagnosis, DSM (Diagnostic and Statistical Manual of Mental Disorders) , and RDoC (Research Domain Criteria) are explained. And the way of clinical application by the multicenter study of COCORO (Cognitive Genetics Collaborative Research Organization) is outlined concerning one of the leading objective auxiliary diagnostic method candidate, cognitive dysfunction in patients with schizophrenia. Finally, diagnostic criteria proposed for a new schizophrenia are introduced including the outlook for the future.

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