http://en.wikipedia.org/wiki/Tetrahydrocannabinol
Studies in animals and in vitro
New scientific evidence is showing that THC can prevent Alzheimer's Disease in an animal model by preventing the inflammation caused by microglia cells which are activated by binding of amyloid protein.[32]
In in-vitro experiments, THC at extremely high concentrations, which could not be reached with commonly-consumed doses, caused inhibition of plaque formation (which are associated with Alzheimer's disease) better than currently-approved drugs.[33]
THC may also be an effective anti-cancer treatment, with studies showing tumor size reduction in mice conducted in 1975[34] and 2007,[35] as well as in a pilot study in humans with glioblastoma multiforme (a type of brain cancer).[36]
A two-year study in which rats and mice were force-fed tetrahydrocannabinol dissolved in corn oil showed reduced body mass, enhanced survival rates, and decreased tumor incidences in several sites, mainly organs under hormonal control. It also caused testicular atrophy and uterine and ovarian hypoplasia, as well as hyperactivity and convulsions immediately after administration, of which the onset and frequency were dose related.[37]
Research in rats indicates that THC prevents hydroperoxide-induced oxidative damage as well as or better than other antioxidants in a chemical (Fenton reaction) system and neuronal cultures.[38] In mice low doses of Δ9-THC reduces the progression of atherosclerosis.[39]
Research has also shown that past claims of brain damage from cannabis use fail to hold up to the scientific method.[40] Instead, recent studies with synthetic cannabinoids show that activation of CB1 receptors can facilitate neurogenesis,[41] as well as neuroprotection,[42] and can even help prevent natural neural degradation from neurodegenerative diseases such as MS, Parkinson's, and Alzheimer's. This, along with research into the CB2 receptor (throughout the immune system), has given the case for medical marijuana more support.[43][44] THC is both a CB1 and CB2 agonist.[45]