This 2006 study came out with some incredible findings about the therapeutic potential of marijuana to both prevent and treat Alzheimer's disease. The researchers discovered that tetrahydrocannabinol (THC) was able to effectively inhibit an enzyme called acetylcholinesterase (AChE), and that it in turn was able to prevent the aggregation of amyloid β-peptide (Aβ), which is induced by AChE. This is so hugely significant because Aβ aggregation is one of the key markers of Alzheimer's disease. Furthurmore, the authors commented that THC was a "considerably superior inhibitor of Aβ aggregation" than prescription drugs which are currently approved for the same purpose.
