The study of BDNF Val66Met polymorphism in Chinese schizophrenic patients.

Accumulating evidence showed that brain-derived neurotrophic factor (BDNF) may be involved in the pathophysiology of schizophrenia. Recent studies have reported that the Val66Met polymorphism of the BDNF gene may be associated with susceptibility for schizophrenia and age of onset of this disease, with mix results. In the present study, the BDNF Val66Met gene polymorphism was examined in 387 inpatients (259 men and 128 women) meeting the DSM-IV criteria for schizophrenia and unrelated 365 healthy controls (255 men and 110 women). The schizophrenia symptomatology was assessed by the Positive and Negative Syndrome Scale (PANSS). Age of onset was defined as the age at which the psychotic symptoms first appeared. Our results showed that genotype frequency distributions and allelic frequencies did not differ between patients and controls. No interaction was found between sex and genotypes. Analysis of covariance (ANCOVA) showed a significance of the BDNF Val66Met genotypes on the age of onset (F=3.76, p<0.02), after adjusting sex, age and duration of illness. Furthermore, ANCOVA showed that the significance of the BDNFVal66Met genotypes on age of onset was increased comparing the Val66Met heterozygotes with the combination of Val66Val and Met66Met homozygotes (F=5.85, p<0.01). Our results suggest that the BDNF Val66Met polymorphism may not contribute directly to the susceptibility to schizophrenia, but to the onset of the disease. Furthermore, our results show the heterozygous effect of the BDNF Val66Met gene on the clinical variability of schizophrenia phenotype.

Smoking initiation and schizophrenia: a replication study in a Chinese Han population.

Schizophrenia is associated with a greater probability of ever smoking daily and with higher rates of initiation of daily smoking after age 20 in Caucasian populations. The aims of the current study were to replicate that schizophrenia is associated with smoking and higher risk of initiating daily smoking before schizophrenia starts among a large sample of male Chinese patients. A survival analysis of onset age for daily smoking compared 776 DSM-IV male inpatients with schizophrenia to 560 male controls. The results showed that the cumulative hazard curves for age of smoking initiation in schizophrenia and controls were significantly different (p<0.001), even after controlling for education (p<0.001). After excluding the patients who started smoking within 5 years before schizophrenia started, the cumulative hazard curve for schizophrenia was significantly different from ever-smoked controls (p<0.001), even after adjusting for education (p<0.001). These findings suggest that schizophrenic patients have a higher risk of starting daily smoking suggesting that vulnerability to schizophrenia may be associated with a higher risk of becoming a daily smoker.