Recent studies have detected similarities between autism spectrum disorder and schizophrenia. We investigated structural abnormalities associated with autistic-like traits in patients with schizophrenia by voxel-based morphometry.

Patients with schizophrenia and healthy subjects were evaluated by the adult version of the social responsiveness scale (SRS-A), which is sensitive to autistic traits and symptoms even under subthreshold conditions, and magnetic resonance imaging.

There were significant decreases in the anterior cingulate cortex, bilateral hippocampi, cerebellums, and right insula of patients with schizophrenia, compared with healthy subjects. We found significant negative correlations of the social communication and interaction (SCI) score, a subscale of SRS-A, with grey matter volume in the left posterior superior temporal region of schizophrenia patients. When subscales of SCI were examined separately in schizophrenic patients, negative correlations were observed between the social cognition score and the volumes of the left posterior superior temporal region, and between social motivation and the posterior cingulate cortex.

We found significant negative correlation between the SCI score and the grey matter volume in the left posterior superior temporal region of schizophrenia patients. This area was the region affected in previous studies of autistic spectrum disorders. Further, this area was associated with the theory of mind. Schizophrenia patients not necessarily show the impairment of SCI, nor this correlated region was not always the point with schizophrenia-specific change. However, we reveal the relationship between the left posterior superior temporal gyrus and the severity of the SCI in schizophrenia by using with SRS-A.

Obesity is a risk factor for psychiatric diseases. Recently, a number of single nucleotide polymorphisms (SNPs) have been shown to be related to body mass index (BMI). In this study, we investigated the association of BMI-related SNPs with psychiatric diseases and one of their endophenotypes, memory performance, in a Japanese population.

The subjects were 1624 patients with one of three psychiatric diseases (799 patients with major depressive disorder, 594 with schizophrenia, and 231 with bipolar disorder) and 1189 healthy controls. Memory performance was assessed using the Wechsler Memory Scale – Revised (WMS-R). Genomic DNA was prepared from venous blood and used to genotype 23 BMI-related SNPs using the TaqMan 5′-exonuclease allelic discrimination assay. We then analysed the relationships between the SNPs and psychiatric disease and various subscales of the WMS-R.

Three SNPs (rs11142387, rs12597579, and rs6548238) showed significant differences in the genotype or allele frequency between patients with any psychiatric diseases and controls. Furthermore, six SNPs (rs11142387, rs12597579, rs2815752, rs2074356, rs4776970, and rs2287019) showed significant differences in at least one subscale of the WMS-R depending on the genotypes of the healthy controls. Interestingly, rs11142387 near the Kruppel-like factor 9 (KLF9) was significantly associated with psychiatric disease and poor memory function.

We identified three and six BMI-related SNPs associated with psychiatric disease and memory performance, respectively. In particular, carrying the A allele of rs11142387 near KLF9 was found to be associated with psychiatric disease and poor memory performance, which warrants further investigations.

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.