What is Marijuana?
Marijuana is a dry, shredded green/brown mix of flowers, stems, seeds, and leaves of the hemp plant Cannabis sativa, it usually is smoked as a cigarette (joint, nail), or in a pipe (bong). It also is smoked in blunts, which are cigars that have been emptied of tobacco and refilled with marijuana, often in combination with another drug such as crack cocaine. It might also be mixed in food or brewed as a tea. As a more concentrated, resinous form it is called hashish and, as a sticky black liquid, hash oil. Marijuana smoke has a pungent and distinctive, usually sweet-and-sour odor. There are countless street terms for marijuana including pot, herb, weed, grass, widow, ganja, and hash, mary jane, or mj as well as terms derived from trademarked varieties of cannabis, such as Bubble Gum, Northern Lights, Fruity Juice, Afghani #1, and a number of Skunk varieties.
The main active chemical in marijuana is THC (delta-9-tetrahydrocannabinol). The membranes of certain nerve cells in the brain contain protein receptors that bind to THC. Once securely in place, THC kicks off a series of cellular reactions that ultimately lead to the high that users experience when they smoke marijuana. The amount of THC (which is also the psychoactive ingredient in hashish) determines the potency and, therefore, the effects of marijuana. Between 1980 and 1997, the amount of THC in marijuana available in the United States rose dramatically.
What Is The Scope Of Marijuana Use In The United States?
In the United States, marijuana is the most commonly used illicit drug. More than 94 million Americans (40%) age 12 and older have tried marijuana at least once, according to the 2003 National Survey on Drug Use and Health (NSDUH). In 2004, 14.6 million Americans age 12 and older used marijuana at least once in the month prior to being surveyed. About 6,000 people a day in 2004 used marijuana for the first time—2.1 million Americans. Of these, 63.8% were under age 18. In the last half of 2003, marijuana was the third most commonly abused drug mentioned in drug-related hospital emergency department (ED) visits in the continental United States, at 12.6%, following cocaine (20%) and alcohol (48.7%).
Marijuana use is widespread among adolescents and young adults. The percentage of middle-school students who reported using marijuana increased throughout the early 1990s. In the past few years, according to the 2004 Monitoring the Future Survey, an annual survey of drug use among the Nation’s middle and high school students, illicit drug use by 8th-, 10th-, and 12th-graders has leveled off. Still, in 2004, 16% of 8th-graders reported that they had tried marijuana, and 6% were current users (defined as having used the drug in the 30 days preceding the survey). Among 10th-graders, 35% had tried marijuana sometime in their lives, and 16% were current users. As would be expected, rates of use among 12th-graders were higher still. Forty-six percent had tried marijuana at some time, and 20% were current users.
The Drug Abuse Warning Network (DAWN), a system for monitoring the health impact of drugs, estimated that, in 2002, marijuana was a contributing factor in over 119,000 emergency department (ED) visits in the United States, with about 15% of the patients between the ages of 12 and 17, and almost two-thirds male.
In 2002, the National Institute of Justice’s Arrestee Drug Abuse Monitoring (ADAM) Program, which collects data on the number of adult arrestees testing positive for various drugs, found that, on average, 41% of adult male arrestees and 27% of adult female arrestees tested positive for marijuana. On average, 57%of juvenile male and 32 percent of juvenile female arrestees tested positive for marijuana.
The National Institute for Drug Abuse (NIDA)’s Community Epidemiology Work Group (CEWG), a network of researchers that tracks trends in the nature and patterns of drug use in major U.S. cities, consistently reports that marijuana frequently is combined with other drugs, such as crack cocaine, PCP, formaldehyde, and codeine cough syrup, sometimes without the user being aware of it.21 Thus, the risks associated with marijuana use may be compounded by the risks of added drugs, as well.
Effects On The Brain
Scientists have learned a great deal about how THC acts in the brain to produce its many effects. When someone smokes marijuana, THC rapidly passes from the lungs into the bloodstream, which carries the chemical to organs throughout the body, including the brain.
In the brain, THC connects to specific sites called cannabinoid receptors on nerve cells and influences the activity of those cells. Some brain areas have many cannabinoid receptors; others have few or none. Many cannabinoid receptors are found in the parts of the brain that influence pleasure, memory, thought, concentration, sensory and time perception, and coordinated movement4.
The short-term effects of marijuana can include problems with memory and learning; distorted perception; difficulty in thinking and problem solving; loss of coordination; and increased heart rate. Research findings for long-term marijuana abuse indicate some changes in the brain similar to those seen after long-term abuse of other major drugs. For example, cannabinoid (THC or synthetic forms of THC) withdrawal in chronically exposed animals leads to an increase in the activation of the stress-response system5 and changes in the activity of nerve cells containing dopamine6. Dopamine neurons are involved in the regulation of motivation and reward, and are directly or indirectly affected by all drugs of abuse.
In a study conducted by the National Highway Traffic Safety Administration, a moderate dose of marijuana alone was shown to impair driving performance; however, the effects of even a low dose of marijuana combined with alcohol were markedly greater than for either drug alone37. Driving indices measured included reaction time, visual search frequency (driver checking side streets), and the ability to perceive and/or respond to changes in the relative velocity of other vehicles.
Marijuana users who have taken high doses of the drug may experience acute toxic psychosis, which includes hallucinations, delusions, and depersonalization – a loss of the sense of personal identity, or self-recognition.10,15 Although the specific causes of these symptoms remain unknown, they appear to occur more frequently when a high dose of cannabis is consumed in food or drink rather than smoked.
Other Health Effects
Marijuana use has been shown to increase users’ difficulty in trying to quit smoking tobacco.38 This was reported in a study comparing smoking cessation in adults who smoked both marijuana and tobacco with those who smoked only tobacco. The relationship between marijuana use and continued smoking was particularly strong in those who smoked marijuana daily at the time of the initial interview, 13 years prior to the followup interview.
A study of 450 individuals found that people who smoke marijuana frequently but do not smoke tobacco have more health problems and miss more days of work than non-smokers do.39 Many of the extra sick days used by the marijuana smokers in the study were for respiratory illnesses.
Even infrequent marijuana use can cause burning and stinging of the mouth and throat, often accompanied by a heavy cough. Someone who smokes marijuana regularly may have many of the same respiratory problems that tobacco smokers do, such as daily cough and phlegm production, more frequent acute chest illnesses, a heightened risk of lung infections, and a greater tendency toward obstructed airways.4
Cancer of the respiratory tract and lungs may also be promoted by marijuana smoke.4 A study comparing 173 cancer patients and 176 healthy individuals produced strong evidence that smoking marijuana increases the likelihood of developing cancer of the head or neck, and that the more marijuana smoked, the greater the increase.17 A statistical analysis of the data suggested that marijuana smoking doubled or tripled the risk of these cancers.
Marijuana has the potential to promote cancer of the lungs and other parts of the respiratory tract because it contains irritants and carcinogens.40 In fact, marijuana smoke contains 50 percent to 70 percent more carcinogenic hydrocarbons than does tobacco smoke.41 It also produces high levels of an enzyme that converts certain hydrocarbons into their carcinogenic form, levels that may accelerate the changes that ultimately produce malignant cells.42 Marijuana users usually inhale more deeply and hold their breath longer than tobacco smokers do, which increases the lungs’ exposure to carcinogenic smoke. These facts suggest that, puff for puff, smoking marijuana may increase the risk of cancer more than smoking tobacco does.
Some adverse health effects caused by marijuana may occur because THC impairs the immune system’s ability to fight off infectious diseases and cancer. In laboratory experiments that exposed animal and human cells to THC or other marijuana ingredients, the normal disease-preventing reactions of many of the key types of immune cells were inhibited.16 In other studies, mice exposed to THC or related substances were more likely than unexposed mice to develop bacterial infections and tumors.14,43
One study has indicated that a person’s risk of heart attack during the first hour after smoking marijuana is four times his or her usual risk.44 The researchers suggest that a heart attack might occur, in part, because marijuana raises blood pressure and heart rate and reduces the oxygen-carrying capacity of blood.
Health Consequences Of Marijuana Abuse
Acute (present durig intoxication)
- Impairs short-term memory
- Impairs attention, judgment, and other cognitive functions
- Impairs coordination and balance
- Increases heart rate
Persistent (lasting longer than intoxication, but may not be permanent)
- Impairs memory and learning skills
Long-term (cumulative, potentially permanent effects of chronic abuse)
- Can lead to addiction
- Increases risk of chronic cough, bronchitis, and emphysema
- Increases risk of cancer of the head, neck, and lungs