Chapter 15: Marijuana

Marijuana is a preparation of leafy material from the Cannabis plant that is smoked.  The active ingredient is also available in oral form.  Marijuana is classified separately because it has unique effects but also shares effects with several other drug groups, including sedatives, analgesics and hallucinogens.

Among several types of Cannabis, the species Cannabis indica is the one primarily grown for its psychoactive properties. Cannabis contains many active chemicals, but the most active is delta-9-tretrahydrocannabinol, or THC.  THC is concentrated in the resin of Cannabis, most of which is found in the flowering tops of the plant. The potency of different Cannabis preparations depends on the amount of resin present.  Hashish, a preparation containing just resin, has the highest concentration of THC.  Lesser amounts are found in sinsemilla, which consists of dried flowering tops of female plants, and in lower-grade marijuana containing just leaves and stems.  The average THC content of U.S. street marijuana is about 2 to 5 percent THC.

Cannabis has a rich history relating to both medicinal and recreational uses.  It originated in China but is now grown worldwide.  It spread through the Muslim world and North Africa and then into Europe and the U.S.  Stories associating the drug with a religious cult that carried out political murders led to its characterization in the U.S. as the "assassin of youth."  By the time the 1937 federal Marijuana Tax Act was passed, all states had laws regulating the use, sale, and/or possession of marijuana.  Usage grew in the 1960’s and 70’s, peaked around 1980, and then declined again until the early 1990s.  There have been some recent state actions to decriminalize possession of small amounts of the drug, but marijuana remains on Schedule I at the federal level.

When smoked, THC is absorbed rapidly and has effects within five (5) to ten (10) minutes.  Oral THC is absorbed slowly and incompletely, and peak effects do not occur until about 90 minutes following ingestion.  THC and its metabolites have long half-lives and may be detectable in the body for several weeks after a large dose of THC.  Two THC receptors have been identified, leading to the discovery of a naturally occurring brain cannabinoid called anandamide.  The receptors are found in many areas of the brain and body, indicating that marijuana can have widespread effects.

Key physiological effects of marijuana include increased heart rate, bronchodilation, reddening of the eyes, and dryness of the mouth and throat. Subjective effects include the "high" most closely associated with marijuana use, along with euphoria, mellowness, and hunger.  Effects are more intense at higher THC concentrations and for less experienced users, who may also experience mild paranoia and hallucinations.  Marijuana use can also impair cognitive performance and alter verbal behavior.

Although strong dependence is not common, it does occur in some individuals, and withdrawal symptoms have been identified.  No overdose deaths have been reported, but marijuana may have acute toxicity potential in its effects on heart rate and driving ability.  Marijuana use also has negative reproductive effects and may impact lung function.  There is no direct evidence that marijuana smoking causes lung cancer, but the smoke does contain carcinogens and additional time and research may be required to make the link to cancer.

Medical use of marijuana has a long and controversial history.  Current research indicates that marijuana may be useful in the treatment of glaucoma, the reduction of nausea in patients undergoing cancer chemotherapy, and the increase of appetite in AIDS patients.  A legal form of THC known as dronabinol is available by prescription.  Medical use of smoked marijuana is currently a violation of federal law, even for seriously ill patients who are using the drug on the advice of their physicians.