EFFECT ON BODY (pathology, pathophysiology)
Marijuana cigarettes contain four to five times as much of certain cancer-causing
substances as tobacco cigarettes. Marijuana has more than 400 different chemicals, many of which are dangerous. It is a dangerous, addictive drug that acts like both a stimulant and a depressant. It makes the heart beat faster, lowers body temperature, increases hunger, slows down the ability to react, and interferes with the proper working of muscles. Marijuana is very harmful, poisoning the structures that trigger cells to grow and replace themselves. Marijuana smokers also seem more likely to get sick than are people who stay away from the drug, so it seems that the drug weakens the body's ability to fight germs. Users have personality problems that include loss of mental energy, lack of interest in everyday things, loss of concentration, and difficulty in recalling events and actions.
The effects of marijuana on each person depend on the type of cannabis, how much THC it contains, the way the drug is taken (by smoking or eating), the experience and expectations of the user, the setting where the drug is used and whether drinking or other drug use is also going on. Some people feel nothing at all when they first try marijuana while others may feel high (intoxicated and/or euphoric). Usually within a few minutes of inhaling marijuana smoke, the user will feel its effects. Along with intoxication, the user will experience a dry mouth, rapid heartbeat, increased appetite, some loss of coordination and poor sense of balance, and slower reaction time. Blood vessels in the eye expand, so the user's eyes look red. For some people, marijuana raises blood pressure slightly and can double the normal heart rate. This effect can be greater when other drugs are mixed with marijuana; but users do not always know when that happens. As the immediate effects fade, usually after 2 to 3 hours, the user may become sleepy.
It is common for marijuana users to feel happy and calm, although depression sometimes occurs. Users become engrossed with ordinary sights, sounds, or tastes, and trivial events may seem extremely interesting or funny. Time seems to pass very slowly, so minutes feel like hours. Sights and sounds become more vivid, imagination increases and random connections between things seem more relevant. Sometimes the drug causes the users to feel thirsty and very hungry - an effect called "the munchies."
A user can also have a bad reaction to marijuana. Some users, especially someone new to the drug or in a strange setting, may suffer acute anxiety, have paranoid thoughts and illusions. This is more likely to happen with high doses of THC. In some cases, true psychosis (loss of contact with reality) occurs, producing paranoid delusions, confusion, and other symptoms. These scary feelings usually disappear within several days as the effects of the drug wear off. In rare cases, a user who has taken a very high dose of the drug can have severe psychotic symptoms and need emergency medical treatment. Other kinds of bad reactions can occur when marijuana is mixed with other drugs, such as PCP or cocaine.
THC in marijuana is readily absorbed by the fatty tissues in various organs. The drug does not dissolve in water, so it can stay in the body for as long as three weeks. Generally, traces (metabolites) of THC can be detected by standard urine testing methods several days after a smoking session. However, in heavy, chronic users, traces can sometimes be detected for weeks after they have stopped using marijuana.
There is evidence that regular users of marijuana can become physically dependent on its effects. Marijuana can be harmful in a number of ways, through both immediate effects and damage to health over time. Marijuana hinders the user's short-term memory (memory for recent events), concentration, learning abilities, and he or she may have trouble handling complex tasks. In 1982, the Georgetown University School of Medicine found that memory loss can stay with teens for up to six weeks after they stop smoking the drug. The drug has also been found to affect speaking and concentration and to slow reaction time. It also leads to a drop in motivation, and this creates poor grades, loss of self-esteem, and loss of career goals. With the use of more potent varieties of marijuana, even performing simple tasks can be difficult. Marijuana also impairs reaction time, perception, judgment, and the coordination and motor skills necessary to drive a car, so users could be involved in auto crashes. The user may experience distorted perception (sights, sounds, time, touch) and have trouble with thinking and problem-solving. There can be loss of coordination and increased heart rate and anxiety. Drug users also may become involved in risky sexual behavior. There is a strong link between drug use and unsafe sex and the spread of HIV, the virus that causes AIDS. Under the influence of marijuana, students may find it hard to study and learn. Young athletes could find their performance is off; timing, movements, and coordination are all affected by THC. Another damaging effect of regular marijuana use by teens is that it can slow down the body's rate of development by lowering the level of hormones the body produces.
ORGAN SYSTEMS MOST AFFECTED BY THIS SUBSTANCE
As marijuana is inhaled and held in the lungs, repeated use can damage the lungs and heart. Marijuana users may have many of the same respiratory problems that tobacco smokers have, such as chronic bronchitis and inflamed sinuses. While all of the long-term effects of marijuana use are not yet known, there are studies showing serious health concerns. For example, a group of scientists in California examined the health status of 450 daily smokers of marijuana but not tobacco. They found that the marijuana smokers had more sick days and more doctor visits for respiratory problems and other types of illness than did a similar group who did not smoke either substance. As to long-term effects of marijuana use, findings so far show that the regular use of marijuana or THC may play a role in cancer and problems in the respiratory, immune, and nervous systems.
It is hard to find out whether marijuana alone causes cancer because many people who smoke marijuana also smoke cigarettes and use other drugs. Marijuana smoke contains some of the same cancer-causing compounds as tobacco, sometimes in higher concentrations. Studies show that someone who smokes five joints per week may be taking in as many cancer-causing chemicals as someone who smokes a full pack of cigarettes every day. Tobacco smoke and marijuana smoke may work together to change the tissues lining the respiratory tract. Marijuana smoking could contribute to early development of head and neck cancer in some people.
Our immune system protects the body from many agents that cause disease. It is not certain whether marijuana damages the immune system of people. But both animal and human studies have shown that marijuana impairs the ability of T-cells in the lungs' immune defense system to fight off some infections. People with HIV and others whose immune system is impaired should avoid marijuana use.
People who smoke marijuana often develop the same kinds of breathing problems that cigarette smokers have. They have symptoms of daily cough and phlegm (chronic bronchitis) and more frequent chest colds. They are also at greater risk of getting lung infections such as pneumonia. Continued marijuana smoking can lead to abnormal function of the lungs and airways. Scientists have found signs of lung tissue that was injured or destroyed by marijuana smoke.
Marijuana smoking also affects the brain and leads to impaired short-term memory, perception, judgment, attention, learning, and motor skills. THC affects the nerve cells in the part of the brain where memories are formed. This makes it hard for the user to recall recent events (such as what happened a few minutes ago). It is hard to learn while high -- a working short-term memory is required for learning and performing tasks that call for more than one or two steps. Among a group of long-time heavy marijuana users in Costa Rica, researchers found that the people had great trouble when asked to recall a short list of words (a standard test of memory). People in that study group also found it very hard to focus their attention on the tests given to them.
Smoking marijuana causes some changes in the brain that are like those caused by cocaine, heroin, and alcohol. Some researchers believe that these changes may put a person more at risk of becoming addicted to other drugs, such as cocaine or heroin. Long-term studies of high school students and their patterns of drug use show that very few young people use other illegal drugs without first trying marijuana. For example, the risk of using cocaine is 104 times greater for those who have tried marijuana than for those who have never tried it. Using marijuana puts children and teens in contact with people who are users and sellers of other drugs. So there is more of a risk that a marijuana user will be exposed to and urged to try more drugs.
Many researchers fear that marijuana damages brain cells, and the long-term effects are still being researched. In laboratory research, scientists found that high doses of THC given to young rats caused a loss of brain cells such as that seen with aging. At 11 or 12 months of age (about half their normal life span), the rats' brains looked like those of animals in old age. It is not known whether a similar effect occurs in humans. Researchers are still learning about the many ways that marijuana could affect the brain.
Scientists do not yet know how the use of marijuana relates to mental illness. Some researchers in Sweden report that regular, long-term intake of THC (from cannabis) can increase the risk of developing certain mental diseases, such as schizophrenia. Others maintain that regular marijuana use can lead to chronic anxiety, personality disturbances, and depression. Some frequent, long-term marijuana users show signs of a lack of motivation (amotivational syndrome). Their problems include not caring about what happens in their lives, no desire to work regularly, fatigue, and a lack of concern about how they look. As a result of these symptoms, some users tend to perform poorly in school or at work.
SECONDARY EFFECTS OF MARIJUANA USE
Marijuana has adverse effects on many of the skills for driving a car. Driving while high can lead to car accidents. This is because marijuana affects many skills required for safe driving: alertness, the ability to concentrate, coordination, and reaction time. These effects can last up to 24 hours after smoking marijuana. Marijuana use can make it difficult to judge distances and react to signals and sounds on the road. There is data showing that marijuana can play an important role in crashes. When users combine marijuana with alcohol, as they often do, the hazards of driving can be more severe than with either drug alone.
A study of patients in a shock-trauma unit who had been in traffic accidents revealed that 15 percent of those who had been driving a car or motorcycle had been smoking marijuana, and another 17 percent had both THC and alcohol in their blood. In one study conducted in Memphis, TN, researchers found that, of 150 reckless drivers who were tested for drugs at the arrest scene, 33 percent tested positive for marijuana, and 12 percent tested positive for both marijuana and cocaine. Data also show that while smoking marijuana, people show the same lack of coordination on standard "drunk driver" tests as do people who have had too much to drink.
Doctors advise pregnant women not to use any drugs because they might harm the growing fetus. One animal study has linked marijuana use to loss of the fetus very early in pregnancy. Some scientific studies have found that babies born to marijuana users were shorter, weighed less, and had smaller head sizes than those born to mothers who did not use the drug. Smaller babies are more likely to develop health problems. Other scientists have found effects of marijuana that resemble the features of fetal alcohol syndrome. There are also research findings that show nervous system problems in children of
mothers who smoked marijuana.
Researchers are not certain whether a newborn baby's health problems, if they are caused by marijuana, will continue as the child grows. Preliminary research shows that children born to mothers who used marijuana regularly during pregnancy may have trouble concentrating. When a nursing mother uses marijuana, some of the THC is passed to the baby in her breast milk. This is a matter for concern, since the THC in the mother's milk is much more concentrated than that in the mother's blood. One study has shown that the use of marijuana by a mother during the first month of breastfeeding can impair the infant's motor development (control of muscle movement).
CLINICAL ASPECTS OF THIS SUBSTANCE
There has been much debate in the media about the possible medical use of marijuana. Under U.S. law since 1970, marijuana has been a Schedule I controlled substance. This means that the drug, at least in its smoked form, has no commonly accepted medical use. In considering possible medical uses of marijuana, it is important to distinguish between whole marijuana and pure THC or other specific chemicals derived from cannabis. Whole marijuana contains hundreds of chemicals, some of which are clearly harmful to health.
THC, the active chemical in marijuana, is manufactured into a pill that is taken by mouth, not smoked. It can be used for treating the nausea and vomiting that go along with certain cancer treatments and is available by prescription. Another chemical related to THC (nabilone) has also been approved by the Food and Drug Administration for treating cancer patients who suffer nausea. The oral THC is also used to help AIDS patients eat more to keep up their weight. Scientists are studying whether marijuana, THC, and related chemicals in marijuana (called cannabinoids) may have other medical uses. According to scientists, more research needs to be done on marijuana's side effects and potential benefits before it can be recommended for medical use.
