Cannabis is the most widely used illegal substance in the world with an estimated 200 to 300 million regular users and has a long history of use for recreational as well as medicinal and religious purposes.
The cut and dried leaves, flowering tops, and stems of the Indian hemp plant (Cannabis sativa) are referred to as marijuana, whereas the dried resin from the plant is known as hashish. The main active ingredient in these forms of cannabis is delta-9-tetrahydrocannabinol, or “THC.”
Marijuana was introduced in the United States in the 1920s and 1930s. Its use was relegated mostly to fringe segments of the population until the 1960s when it was incorporated into the youth counterculture.
Marijuana use peaked in 1978 when up to 10 percent of surveyed high school students reported using daily and then went on the decline until 1992 where 1.9 percent reported daily use. However, since 2003, surveys suggest that marijuana use is again on the rise.
Patters of marijuana use vary widely, ranging from people who have tried it once or twice with or without inhaling, to intermittent users who may smoke one or two joints weekly or monthly, to heavy daily users who have severe problems with dependence or abuse.
Like alcohol, the proportion who progress from use of marijuana to dependence on it ir relatively low. However, most users of so called hard drugs starts first with marijuana and some people have their lives totally ruined by marijuana dependence.
Marijuana and hashish are usually smoked to produce a high that begins in approximately 10 to 20 minutes and lasts for a few hours. When consumed orally, the intoxication takes several hours to begin, lasts considerably longer, and often results in more intense psychoactive effects.
Cannabis intoxication is characterized by euphoric “high” feeling, grandiosity, inappropriate laughter, heightened introspection, and sedation. Perceptual changes are common there may be a subjective sense that time has slowed down and that colors or sounds are more intense and vivid. At high doses, there may be intense feelings of being unreal or that the external world is unreal, panic attacks, paranoid delusions, or even frank hallucinations.
Physiological signs of cannabis intoxication include rapid pulse, dry mouth, increased appetite, and reddening of the eyes. Tolerance to the effects of marijuana is very variable some users have to increase their frequency of use, but most do not.
A well defined withdrawal syndrome has not been clearly established, but some heavy users develop symptoms of restlessness, irritability, insomnia, nausea, diarrhea, and chills following abrupt discontinuation.
Cannabis intoxication markedly impairs recall, inhibits ability to store memory, reduces attention, makes it more difficult to verbalize thoughts, and inhibits one’s ability to perform goal directed tasks that require multiple steps. Marijuana use at school, work, or while performing complicated tasks can have disastrous consequences. There is no convincing evidence of cognitive impairment once the acute effects of the THC wear off.
The long term effects of marijuana on behavior are controversial. There is little question that some particularly heavy marijuana users have a so called “motivational syndrome” characterized by apathy, social withdrawal, and poor concentration.
The problem here is establishing cause and effect. Do these symptoms result from chronic heavy use or are the people who are characterologically unmotivated predisposed to fill their otherwise empty lives with a marijuana high?
The most likely explanation is some combination of both. Laboratory studies have raised concerns about possible long term health effects of heavy use. There is little question that marijuana smoke cause lung diseases, including bronchitis and asthma. Joints contain much more tar than tobacco smoke and in animals are much more carcinogenic.