Cannabinoids are certain chemical compounds found only in cannabis. Delta-9 tetrahydrocannabinol is (THC) is the most commonly recognized. This is what gives users that telltale euphoric feeling. THC may also play a role, should medical marijuana continue to become mainstream, as a painkiller. In fact, one study found that those states that passed a medical marijuana law saw a drop in opioid painkiller-related deaths.