BDNF and Cognitive impairment: Firstly, decreased GSH and oxidative stress are implicated in the cognitive decline associated with both normal aging and neurodegenerative disorders.23 Secondly, reduced GSH has been associated with depletion in brain-derived neurotrophic factor (BDNF) and N-methyl-d-aspartate (NMDA) hypo-function, both of which are associated with cognitive impairment.