METHODS: Studies from 1964 to 2020 (for oxidative DNA damage) and from 1907 to 2021 (for ROS) in Pubmed and Scopus databases were selected and analysed using Comprehensive Meta-Analysis version 2 respectively. Data were subjected to meta-analysis for examining the effect sizes of the results. Publication bias assessments, heterogeneity assessments and subgroup analyses based on biological specimens, patient status, illness duration and medication history were also conducted.
RESULTS: This meta-analysis revealed that oxidative DNA damage was significantly higher in patients with schizophrenia and bipolar disorder based on random-effects models whereas in depressed patients, the level was not significant. Since heterogeneity was present, results based on random-effects model was preferred. Our results also showed that oxidative DNA damage level was significantly higher in lymphocyte and urine of patients with schizophrenia and bipolar disorder respectively. Besides, larger effect size was observed in inpatients and those with longer illness duration and medication history. Significant higher ROS was also observed in schizophrenic patients but not in depressive patients.
CONCLUSION: The present meta-analysis found that oxidative DNA damage was significantly higher in schizophrenia and bipolar disorder but not in depression. The significant association between deoxyguanosines and mental illnesses suggested the possibility of using 8-OHdG or 8-oxodG as biomarker in measurement of oxidative DNA damage and oxidative stress. Higher ROS level indicated the involvement of oxidative stress in schizophrenia. The information from this study may provide better understanding on pathophysiology of mental illnesses.
MATERIALS AND METHODS: We searched candidate genes from the schizophrenia database and performed a comprehensive meta-analysis using all the available data up to August 2017. The association between susceptible SNPs and schizophrenia was assessed by the pooled odds ratio with 95% confidence interval using fixed-effect and random-effect models.
RESULTS: A total of 21 studies including 8291 cases and 9638 controls were used for meta-analysis. Three investigated SNPs were rs165599, rs3737597, and rs1047631 of COMT, DISC1, and DTNBP1, respectively. Our results suggested that rs3737597 showed a significant association with schizophrenia in Europeans (odds ratio: 1.584, P: 0.002, 95% confidence interval: 1.176-2.134) under a random-effect framework.
CONCLUSION: This meta-analysis indicated that rs3737597 of DISC1 was significantly associated with schizophrenia in Europeans, and it can be suggested as an ethnic-specific risk genetic factor.
METHOD: In this study, we investigated this controversial association between the Ser9Gly (A/G) polymorphism and SCZ using Malay cases-control (261 cases/157 controls) samples. PCR-RFLP was performed to genotype the distribution of the DRD3 Ser9Gly polymorphism.
RESULTS: Both healthy control and SCHZ patient groups were in of Hardy-Weinberg equilibrium for the analyzed genetic variability. There was a significant association between the genotype distribution DRD3 polymorphisms and SCZ (χ(2)= 9.359; df = 2; P = 0.009).
CONCLUSION: We believe that further studies are required to examine the association between others dopamine-related genes and the behavioral phenotypes of SCZ.
METHODS: PubMed and PsycARTICLES databases were searched for the studies published between January 1985 and November 2017. Data were drawn from 19 studies encompassing 1095 patients and 324 controls. The effect size and heterogeneity were assessed with Comprehensive Meta-Analysis version 2 using random-effect model.
RESULTS: Overall, the results showed that the schizophrenia patients performed significantly (p<0.001) worse than healthy controls in both TMT-A and B. However, concurrent substance abuse, clinical status (inpatient or outpatient), duration of education and duration of illness were not associated with cognitive impairment among the schizophrenia patients.
CONCLUSION: The present meta-analysis confirmed the cognitive processing speed and flexibility of schizophrenia patients were impaired. However, their duration of education, duration of illness and clinical status (inpatient or outpatient) were not the risk factors.