Antioxidants seem to be all the rage these days. However, long before "antioxidant" became the major buzzword that it is now, scientists in this 1998 study took a look at the antioxidant and neuroprotective properties of the cannabinoids found in marijuana, namely tetrahydrocannabinol and cannabidiol. They found that, in rats, THC and CBD were both able to reduce toxic levels of the neurotransmitter known as glutamate, and that they were able to prevent the oxidative damage of hydrogen peroxide as well.
