This is the 2007 version. Click here for the 2017 chapter 03 table of contents.


Marijuana is derived from the cannabis sativa or cannabis indicus plant. Historically it has been smoked, put into teas, or eaten. Since the late 1990s vaporization or volatilization (extracting the active ingredients with hot air) has become increasingly common. Marijuana smoking reached a peak of popularity in the United States during the late 1960s and early 1970s, when soldiers, blue-collar workers, and college students used it most widely. Overall levels of marijuana use in the United States declined in the 1980s, went up again in the early 1990s, declined again in the mid 1990s, and went up again in 2000s.

Some drugs, such as PCP and methaqualone, seem to have a single peak of high usage and then disappear. Those drugs have key components that must be manufactured in sophisticated laboratories. Therefore governments working together with phamaceutical companies can eliminate access to crucial ingredients. Other drugs, like heroin, cocaine, and marijuana, do not require sophisticated chemicals. Their popularity goes through cycles that depend on factors like cost, availability, law enforcement efforts, and how the drugs are portrayed in mass media.

What is marijuana? Hashish? Anandamide?

Marijuana resembles a brain chemical called anandamide, discovered in 1988. The researchers who discovered anandamide concluded that it was responsible for the reinforcing effects of marijuana. They put the word ananda (the Sanskrit word for bliss) in the chemical's name. Scientists use the term cannabinoids to describe anadamide and similar psychoactive compounds found in marijuana. Cannabinoids appear in brain areas such as the frontal lobes and hippocampus, a pattern unlike other psychoactive drugs. Receptors for these chemicals are found in both the brain and the spleen of many species, from sea urchins to rats to humans, suggesting an "ancient-and widespread-signaling system for organisms." (Pennisis, 1993)

What happens when the receptors for anandamide are missing, in mice?

One line of mutant mice lacks the receptors for anandamide and related compounds (the central cannabinoid receptors). Consequently, they do not respond to cannabinoid drugs. They also do not find opiates reinforcing, and if forced to become addicted to opiates, they experience fewer withdrawal symptoms than normal. Researchers suggest that drugs might be developed to help heroin addicts by blocking the central cannabinoid receptors (Ledent, Valverde, Cossu, Petitet, Aubert, Beslot, Bohme, Imperato, Pedrazzini, Roques, Vassart, Fratta & Parmentier, 1999).

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