No linkage or linkage disequilibrium between brain-derived neurotrophic factor (BDNF) dinucleotide repeat polymorphism and schizophrenia in Irish families

There is increasing evidence that a neurodevelopmental process is accountable for at least a proportion of schizophrenic cases. Brain-derived neurotrophic factor (BDNF), a member of a group of proteins that includes neurotrophin-3/4/5 and nerve growth factor (NGF), is an attractive candidate gene. We have performed a case control association study using the BDNF dinucleotide repeat polymorphism in a sample of familial schizophrenic individuals and in healthy, ethnically matched control subjects. We also performed a linkage analysis on 265 multiplex families using the same marker. We found no differences in allele frequencies between the patient and control groups nor any evidence for transmission disequilibrium or linkage with the multiply affected families. We conclude that DNA variation at or near the BDNF gene is unlikely to contribute to the genetic predisposition to schizophrenia.