The most researched cannabinoid is delta-9-tetrahydrocannabinol (THC). THC is responsible for the way your brain and body respond to cannabis, including the high and intoxication. THC has some therapeutic effects but it also has harmful effects. Harmful effects may be greater when the strength of THC is higher. Cannabis that contains very low amounts of THC in its flowers and leaves (less than 0.3%) is classified as hemp.