Influence of Depression on Working Memory Measured by Digit Backward Span in the Subjects with Mild Cognitive Impairment and Dementia

OBJECTIVES: We aimed to explore the influence of depression on working memory in patients with mild cognitive impairment (MCI) and dementia. METHODS: Clinical and neuropsychological data of 43 subjects with mild cognitive impairment (MCI) (n=17) and dementia (n=26) who had visited Department of Psychiatry at Soonchunhyang University Seoul Hospital, were collected. The subjects were divided into depressed (n=18) and non-depressed (n=25) groups based on the Korean version of Short Geriatric Depression Scale. Two-way analysis of variance test was conducted to evaluate the influence of diagnosis (MCI and dementia), the presence of depression and their interaction on working memory which was measured by digit forward and backward span test. RESULTS: Among the patients with MCI, test score of digit backward span test in depressed group was significantly lower than in non-depressed group. However, among the patients with dementia, there was no significant difference in digit backward span test between depressed and non-depressed groups. CONCLUSION: This study suggests that the depression could deteriorate working memory measured by digit backward span test in patients with MCI, relative to in patients with dementia and it also implicates the diagnostic assessment for depression has clinically importance in patients with MCI.

Association Analysis between (AAT)n Repeats in the Cannabinoid Receptor 1 Gene and Schizophrenia in a Korean Population

OBJECTIVES: Previous studies suggest that the cannabinoid receptor 1 (CNR1) gene could be an important candidate gene for schizophrenia. According to linkage studies, this gene is located on chromosome 6q14-q15, which is known to harbor the schizophrenia susceptibility locus (locus 5, SCZ5, OMIM 803175). The pharmacological agent delta-9-tetrahydrocannabinol (Delta-9-THC) seems to elicit the symptoms of schizophrenia. The association between CNR1 polymorphisms and schizophrenia is actively being investigated, and some studies have linked the AAT-trinucleotide repeats in CNR1 to the onset of schizophrenia. In this study, we have investigated the association between the AAT-trinucleotide repeats in CNR1 and schizophrenia by studying schizophrenia patients and healthy individuals from Korea. METHODS: DNA was extracted from the blood samples of 394 control subjects and 337 patients diagnosed with schizophrenia (as per the Diagnostic and Statistical Manual of Mental Disorders, fourth edition criteria). After polymerase chain reaction amplification, a logistic regression analysis, with age and gender as the covariates, was performed to study the variations in the AAT-repeat polymorphisms between the two groups. RESULTS: In total, 8 types of trinucleotide repeats were identified, each containing 7, 8, 10, 11, 12, 13, 14, and 15 repeats, respectively. (AAT)13 allele was most frequently observed, with a frequency of 33.6% and 31.6% in the patient and control groups, respectively. The frequency of the other repeat alleles in the patient group (in the decreasing order) was as follows : (AAT)13 33.6%, (AAT)14 21.6%, (AAT)12 18.5%, and (AAT)7 11.1%. The frequency of the repeat alleles in the control group (in the decreasing order) was as follows : (AAT)13 31.6%, (AAT)14 24.5%, (AAT)12 17.2%, and (AAT)7 11.6%. However, there were no significant differences in the AAT-repeat polymorphisms of the CNR1 gene between the patient group and the control group. CONCLUSIONS: Although our study revealed no significant association of the AAT-repeat polymorphism of the CNR1 gene with schizophrenia, it will serve as a good reference for future studies designed to examine the cannabinoid hypothesis of schizophrenia.

Association Analysis of Neuregulin 3 Gene with Schizophrenia in a Korean Population

OBJECTIVES: Located on chromosome 10q22-q23, the human neuregulin 3 (NRG3) is suggested as a strong positional and functional candidate gene involved in the pathogenesis of schizophrenia. Several case-control studies examining the association between polymorphisms on NRG3 gene with schizophrenia and/or its traits (such as delusion) have been reported recently in cohorts of Han Chinese, Ashkenazi Jews, Australians, white Americans of Western European ancestry and Koreans. Thus, this study aimed to investigate the association of one SNP in exon 9 (rs2295933) of NRG3 gene with the risk of schizophrenia in a Korean population. METHODS: Using TaqMan assay, rs2295933 in the exon 9 of NRG3 was genotyped in 435 patients with schizophrenia as cases and 393 unrelated healthy individuals as controls. Differences in frequency distributions were analyzed using logistic regression models following various modes of genetic inheritance and controlling for age and sex as covariates. RESULTS: Subsequent analysis revealed that the frequency distribution of rs2295933 of NRG3 was not different between schizophrenia patients and healthy controls of Korean ethnicity. CONCLUSIONS: This study does not support the role of NRG3 in schizophrenia in a Korean population.