Yes, you can find plenty of THC in a portion of marijuana. However, in most people's brains, there is just about the right amount of similar chemicals circulating. They are natural, and most people's bodies know how to produce them.
So far, this is a study with mice, but the mice responded well when the endocannabinoids were injected into their brains in areas affected by Parkinson's disease. If this research ever proves to be effective in humans, it will introduce a number of concerns about how to best handle a medicine that has a cousin with a bad reputation.
