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Cannabis is a collective term referring to the bioactive substances from Cannabis sativa. The C. sativa plant contains a group of more than 60 chemicals (C21 group) called cannabinoids. In this chapter, the term cannabis encompasses all cannabis products. The major cannabinoids are cannabinol, cannabidiol, and tetrahydrocannabinol. The principal psychoactive cannabinoid is Δ9-tetrahydrocannabinol (THC). Marijuana is the common name for a mixture of dried leaves and flowers of the C. sativa plant. Hashish and hashish oil are the pressed resin and the oil expressed from the pressed resin, respectively. The concentration of THC varies from 1% in low-grade marijuana up to 50% in hash oil. Pure THC and a synthetic cannabinoid are available by prescription with the generic names of dronabinol and nabilone, respectively.

Cannabis has been used for more than 4000 years. The earliest documentation of the therapeutic use of marijuana is the 4th century BC in China.82 Cannabis use spread from China to India to North Africa, reaching Europe around AD 500.70 In colonial North America, cannabis was cultivated as a source of fiber.

Marijuana was used as an intoxicant from the 1850s until the 1930s when the US Federal Bureau of Narcotics began to portray marijuana as a powerful, addicting substance. Despite this, marijuana was listed in the United States Pharmacopoeia from 1850 to 1942. In 1970, The Controlled Substances Act classified marijuana as a Schedule I drug.

In all populations, cannabis use by males exceeds use by females. Currently, marijuana is the most commonly used illicit xenobiotic in the United States. A recent study by the Substance Abuse and Mental Health Services Administration117 reported that in 2006 in the United States, 6.0% (14.8 million persons) ≥12 years used marijuana in the month prior to the survey; this prevalence is unchanged from previous years. The prevalence of past-month users aged 12 to 17 years was 6.7% (down from 8.2% in 2002). The number of first-time users was estimated to be 2.1 million, with 63.3% less than 18 years of age.

In 2004 in Europe, a mean of 20% (range 5%–31%) of people aged 15 to 64 years have used cannabis at least once in their lifetime; the general trend increased from the early 1990s to the early 2000s. Past-year use ranges from 1.7% to 10.4% and past-month use ranges from 0.5% to 6.2%; approximately 25% (range 19%–33%) of those who used at least once in the last month use it daily (~3 million daily users).29

In 2004 in Australia, 33.6% of people ≥14 years of age had used cannabis at least once in their life (unchanged from previous years) and 11.3% had used cannabis within the past year (down from a high of 17.9% in 1998).4

Cannabinoids are proposed for use in the management of many clinical conditions (Table 83–1), but have generally only been approved for ...

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