Failure to find associations of the CA repeat polymorphism in the first intron and the Gly(-63)/Glu(-63) polymorphism of the neurotrophin-3 gene with schizophrenia

This study aimed to replicate positive associations between polymorphisms of the neurotrophin-3 gene and schizophrenia, The reported associations, which were the results of searching for mutations in the locus in schizophrenics under the hypothesis of neurodevelopmental etiology of schizophrenia, are that the states carrying the (CA)(23) allele of the CA repeat in the first intron have a 2.56-fold increased risk of schizophrenia and those carrying the allele Glu(-63) instead of Cry(-63) have a 2.6-fold increased risk of schizophrenia with onset before 25 years and with duration of the illness of more than 10 years. We analyzed these polymorphisms in 80 schizophrenics with onset before 25 years of age and with duration of illness of more than 10 years and 80 age-matched psychosis-free controls. With our sample size, there was a 90% chance of detecting odds ratios observed in initial positive reports. We found similar allele and genotype frequencies of both polymorphisms between the schizophrenic and control groups. We failed to support associations between the polymorphisms of the neurotrophin-3 gene analyzed and schizophrenia.