Brain-derived neurotrophic factor, also known as BDNF, is a member of the "neurotrophin" family of growth factors, which are related to the canonical "Nerve Growth Factor", NGF. BDNF acts on certain neurons of the central nervous system and the peripheral nervous system, helping to support the survival of existing neurons, and encourage the growth and differentiation of new neurons and synapses. BDNF is actually found in a range of tissue and cell types, not just in the brain. It is also expressed in the retina, the central nervous system, motor neurons, the kidneys, and the prostate. Various studies have shown possible links between BDNF and conditions such as depression, bipolar disorder,schizophrenia, obsessive-compulsive disorder, Alzheimer's disease, Huntington's disease, Rett syndrome, and dementia, as well as anorexia nervosa and bulimia nervosa.