It appears that Levodopa administration in those with Parkinson's disease will deplete methylation (SAMe), and thus increase homocysteine, which is a neurotoxin. Additionally, depletion of methylation is associated with depression, commonly seen in Parkinson's disease
There is significant evidence that the pathogenesis of several neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, Friedreich's ataxia (FRDA), multiple sclerosis and amyotrophic lateral sclerosis, may involve the generation of reactive oxygen species (ROS) and/or reactive nitrogen species (RNS) associated with mitochondrial dysfunction