For many decades marijuana has been the most widely used illicit drug in the United States. A derivative of the Indian hemp plant, it contains hundreds of chemical components. However, the "appeal" for the drug comes through levels of THC contained in the plant's leaves and stems. These vary in the plants from very small trace amounts to as much as 5% in agriculturally developed products intended for smokers. Special refinements can increase THC to nearly 50% in some hash oils.

THC is not the simple drug many people claim it to be. Cannabis and its stronger variety, sinsemilla, are sources for hashish, "black tar," and hash oil. Hashish is an ancient hallucinogenic and as with all THC based drugs, it can induce severe paranoia and intense anxiety. Research on nearly all marijuana and its derivatives has been extensive in the past twenty years. Conclusions indicate THC can disrupt or reduce short-term memory, adversely effect ability to concentrate and cause disorientation in such tasks as operating a vehicle.

Long considered the first indicator for later substance abuses, extensive study has failed to prove that point, however psychological dependencies have been documented. Alterations in the brain of long-term users have been compared similar to those encountered with persons abusing other more addictive substances.

Frequently used in conjunction with alcohol and other drugs, marijuana can induce added stress on the physical health of the user. Heart rate and blood pressure have been detected at much higher levels when marijuana is added to other drugs. The consequence is greater effect on the cardiovascular system and longer time needed to return to normal levels. When smoked marijuana is unfiltered and lung damage can be comparable to that experienced by cigarette smokers. The amount of tar inhaled by marijuana smokers is four to five times greater than that found with cigarette use.