Marijuana, or cannabis, is a crude preparation of flowering tops, leaves, seeds, and stems of female plants of the Indian hemp Cannabis sativa; and it is usually smoked as a “recreational” drug. The intoxicating constituents of hemp are found in the resin exuded by the tops of the plants, particularly the females. Male plants produce only a small amount of resin. The resin itself, when prepared for smoking or eating, is known as “hashish.”

Various cannabis preparations are used as intoxicants throughout the world, with potency varying with the amount of resin present. The tops contain the most resin; stems, seeds, and lower leaves the least. The intoxicants in the resin are called cannabinoids, the most active of which is delta 9-tetrahydrocannabinol (THC).Although marijuana use in the United States dates back to the 19th century, its early use was confined predominantly to certain groups such as Mexican laborers, inner city Blacks, and some “Bohemian” groups.

Restricted by increasingly severe legal penalties imposed during the 1930s, its use in those relatively small groups was not a major cause for public concern. Following the widespread popularity and use of the hallucinogen LSD during the 1960s, an explosion in marijuana use took place, at first on college campuses, followed by downward spread to secondary schools and upward to portions of the middle class. Public alarm grew over the hazards to the general public posed by the rapidly growing use of marijuana and other mind-altering drugs. Marijuana, plus other drugs like heroin, had a high potential for abuse with limited or no potential for medical use, and they were designated as schedule I drugs ˆ making their use and possession illegal.

The scheduling of dangerous drugs is done by the Drug Enforcement Administration (DEA), but only after the Food and Drug Administration (FDA) decides that a new drug is a suitable medication, albeit one needing to be scheduled because of its abuse potential. The agencies work closely together, as required by law, and a routine scheduling action cannot be taken by one of the agencies without the concurrence of the other.Recent developmentsDuring the past two decades in the United States, there has been a steady increase in the number of people entering treatment for marijuana related problems.

According to one report, two-thirds of those admitted for treatment were young ˆ between the ages of 12 and 25 years (1). The majority of those admissions were from either the justice or educational systems.Marijuana use is associated with impaired educational attainment (2), reduced workplace productivity (3), and plays a major role in motor vehicle accidents (4). Marijuana is increasingly recognized as a cause, along with tobacco, of both lung cancer and emphysema (5) (6). In spite of this, an editorial in a major medical journal, the Lancet, stated as recently as 1995 that “the smoking of cannabis, even long term, is not harmful to health.”(7).In the United States, marijuana use remained stable at about 4% during the decade between 1991-1992 and 2001-2002, according to two large national surveys conducted 10 years apart (8). Marijuana use disorders among adults, however, increased significantly during that decade. The potency of THC in confiscated marijuana increased by 66% between 1992 and 2002, and this may have contributed to the problem.

The disorders included marijuana abuse, that is, use under hazardous conditions or impairment in social, occupational, or educational functioning related to use. Another marijuana use disorder is dependence, defined as increased tolerance, compulsive use, impaired control, and continued use despite physical and psychological problems caused by its use.A major focus for concern has been the extent to which marijuana use leads to the use of and dependence on “hard” drugs. There has been a longstanding debate over whether this association is due to the criminalization of marijuana use, forcing the user to seek suppliers who deal in other illicit drugs, or whether marijuana conditions the user to try other drugs.A study was reported from Australia of a volunteer sample of 311 young, adult, monozygotic and dizygotic, same sex twins discordant for early cannabis use i.e. less than 17 years (1). The outcome measures included subsequent non-medical use of prescription sedatives, hallucinogens, cocaine or other stimulants, and opioids leading to abuse or dependence on these drugs. Abuse and/or dependence on cannabis or alcohol were also outcome measures.