The brain derived neurotrophic factor and influences of stress in depression.

Brain derived neurotrophic factor (BDNF) is a member of the neurotrophin family and is widely expressed throughout the central nervous system (CNS). BDNF is involved in proliferation, differentiation, survival and death of neuronal and non-neuronal cells in the developing and adult CNS. The BDNF hypothesis of depression postulates that a reduction in BDNF is directly involved in the pathophysiology of depression, whilst anti-depressant mediated restoration of BDNF is responsible for the alleviation of the depressive state. This hypothesis is drawn from several studies implicating BDNF in depression and has received considerable support, which will be reviewed in this paper. This review will also discuss the implications of the functional Val66Met polymorphism of the gene encoding BDNF, which may reduce BDNF expression particularly when exposed to stress and thus may play a critical role in the pathogenesis of depression.