title: Relationship between brain-derived neurotrophic factor gene C270T polymorphisms and the psychotic symptoms and cognitive functioning of patients with schizophrenia.
abstract: BACKGROUND
  Findings from previous studies linking brain-derived neurotrophic factor (BDNF) and schizophrenia are inconsistent and few studies have assessed the relationship between BDNF C270T gene polymorphisms and the clinical and cognitive symptoms of schizophrenia.
  
  
  OBJECTIVE
  Compare the prevalence of the BDNF C270T gene polymorphisms between patients with schizophrenia and controls and, in the patients, assess the relationship of genotypes to the severity of symptoms.
  
  
  METHODS
  BDNF C270T genotype and allele frequency were measured using Polymerase Chain Reaction methods in 224 drug-free patients with schizophrenia and 220 controls. Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS), and cognitive functioning was assessed using the Wisconsin Card Sorting Test (WCST) and the Trail Making Test (TMT). In the patient group, differences in severity of symptoms across the three genotypes (i.e., C/C, C/T, and T/T) of C270T were assessed using one-way analysis of variance.
  
  
  RESULTS
  The frequency of the T allele was much higher in patients than in controls (15.6% vs. 4.3%, χ(2)=31.47, p<0.001) and the C/T genotype was more common among patients than controls (27.7% vs. 7.7%, χ(2)=34.93, p<0.001). Compared to controls, patients performed poorly on all the cognitive tests, but there were no significant differences in the cognitive measures between patients with the three different genotypes. The total PANSS score, the PANSS negative symptoms subscale score, and the PANSS general psychopathology subscale score were not significantly different between the three groups of patients. However, the PANSS positive symptoms subscale score showed a small, statistically significant elevation in the severity of positive symptoms in the C/T genotype compared to the C/C genotype.
  
  
  CONCLUSIONS
  We confirm previous findings about differences in the prevalence of the BDNF C270T gene polymorphisms in schizophrenia, but do not find strong evidence of a relationship between different genotypes and the severity of the clinical or cognitive symptoms of schizophrenia. Clinical and cognitive symptoms in schizophrenia fluctuate over the course of the illness and with treatment, so stable, individual-specific measures of these parameters (that is, traits) need to be identified before it will be possible to definitively assess their relationship to different genotypes.
authors.affiliation: School of Mental Health, Jining Medical University, Jining, Shandong Province, China.
authors.forename: Jinguo
authors.initials: J
authors.lastname: Zhai
authors.affiliation: Institute of Mental Health, Second Xiangya Hospital,Central South University, Changsha, Hunan Province,China.
authors.forename: Jingping
authors.initials: J
authors.lastname: Zhao
authors.affiliation: School of Mental Health, Jining Medical University, Jining, Shandong Province, China.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University,Beijing, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Psychiatry,Second Affiliated Hospital, Jining Medical University,Jining,Shandong Province,China.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Su