If someone is high on marijuana, he or she might:
- Seem dizzy and have trouble walking
- Seem silly and giggly for no reason
- Have very red, bloodshot eyes
- Have a hard time remembering things that just happened
- Become very sleepy after a few hours, as the early effects fade
The effects of marijuana on each person depend on the type of cannabis and 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 alcohol or other drugs are also being used. Some people feel nothing at all when they first try marijuana; others may feel high (intoxicated and/or euphoric).
It's common for marijuana users to 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. Sometimes the drug causes users to feel thirsty and very hungry—an effect called "the munchies."
Regarding children, parents should be aware of changes in a child's behavior, although this may be difficult with teenagers. Parents should look for withdrawal, depression, fatigue, carelessness with grooming, hostility and deteriorating relationships with family members and friends. In addition, changes in academic performance, increased absenteeism or truancy, lost interest in sports or other favorite activities, and changes in eating or sleeping habits could be related to drug use. However, these signs may also indicate problems other than use of drugs.
In addition, parents should be aware of:
- Signs of drugs and drug paraphernalia, including pipes and rolling papers
- Odor on clothes and in the child's bedroom
- Use of incense and other deodorizers
- Use of eye drops
- Clothing, posters, jewelry promoting drug use
Unpleasant effects that may occur include depersonalization (inability to distinguish oneself from others), changed body image, disorientation, and acute panic reactions or severe paranoia.
Some cases of severe delirium, hallucinations, and violence have also been reported, though such cases should raise suspicion that the marijuana may have been laced with another agent, such as PCP.
Marijuana has specific effects that may decrease a user's ability to perform tasks requiring a great deal of coordination (such as driving a car). Visual tracking is impaired, and the sense of time is typically prolonged.
Learning may be greatly affected because the drug reduces a user's ability to concentrate. Studies have shown that learning may become "state-dependent," meaning that information acquired or learned while under the influence of marijuana is best recalled in the same state of drug influence.
Other marijuana effects may include:
- Blood-shot eyes
- Increased heart rate and blood pressure
- Bronchodilatation (widening of the airways)
- In some users, bronchial (airway) irritation leading to bronchoconstriction (narrowing of the airways) or bronchospasm (airway spasms, leading to narrowing of the airways)
- Pharyngitis, sinussitis, bronchitis, and asthma in heavy users
- Possible serious effects on the immune system
Length of Time Present in Body
Regular marijuana users, upon stopping use of the drug, may experience withdrawal effects. These may include agitation, insomnia, irritability, and anxiety.
Additionally, fatty tissues in various organs readily absorb the THC in marijuana. 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.
Harmful 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), and he or she may have trouble handling complex tasks. With the use of more potent varieties of marijuana, even simple tasks can be difficult.
Because of the drug's effects on perceptions and reaction time, users could be involved in auto crashes. 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.
Under the influence of marijuana, students may find it hard to study and learn. Young athletes could find their performances are off; timing, movements and coordination are all affected by THC.
Effects on Driving
Marijuana affects many skills required for safe driving: alertness, good concentration and coordination, and quick reaction time. These effects can last up to 24 hours after smoking marijuana. Marijuana use can make it difficult to judge distances as well as react to signals and other sights and sounds on the road.
Studies show that approximately 6 to 11 percent of fatal-accident victims tested positive for THC. In many of these cases, alcohol was detected as well. When users combine marijuana with alcohol, as they often do, the hazards of driving can be more severe than with either drug alone. 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 alone.
In one study, researchers found that out of 150 reckless drivers who were tested for drugs at an arrest scene, 33 percent tested positive for marijuana and 12 percent tested positive for both marijuana and cocaine. Data also shows that after smoking marijuana, people demonstrate the same lack of coordination on standard drunken-driver tests as do people who have had too much to drink.
Long-term Effects of Marijuana
While all of the long-term effects of marijuana use are not yet known, there are studies raising serious health concerns. For example, one study examined the health statuses of 450 daily non-tobacco marijuana smokers. They found that the marijuana smokers had more sick days and more doctor visits for respiratory and other problems than did a similar group who did not smoke either substance.
Findings show that the regular use of marijuana may play a role in cancer and problems in the respiratory and immune systems.
Cancer
It is hard to find out whether marijuana alone can cause 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 day 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 tissue lining of the respiratory tract. Marijuana smoking could contribute to early development of head and neck cancer in some people.
Lungs and Airways
People who smoke marijuana regularly may develop many of the same breathing problems that tobacco smokers have, such as daily cough and phlegm production, more frequent chest colds, a heightened risk of lung infections and a greater tendency toward obstructed airways. Cancer of the respiratory tract and lungs may also be promoted by marijuana smoke, since it contains irritants and carcinogens. Marijuana smokers usually inhale more deeply and hold their breath longer than tobacco smokers, which increases the lungs' exposure to carcinogenic smoke. Thus, puff for puff, smoking marijuana may increase the risk of cancer more than smoking tobacco does.
Immune System
The immune system protects the body from many agents that cause disease. It is not certain whether marijuana damages the immune systems 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.
Effects on Pregnancy
Doctors advise pregnant women not to use any drugs because they might harm the growing fetus. Although one animal study has linked marijuana use to loss of the fetus very early in pregnancy, two studies in humans found no association between marijuana use and early pregnancy loss. More research is necessary to fully understand the effects of marijuana use on pregnancy.
Some scientific studies have found that babies born to women who use marijuana during their pregnancies display altered responses to visual stimulation, increased tremors and a high-pitched cry, which may indicate problems with nervous system development. During pre- and early school years, marijuana-exposed children have been reported to exhibit more behavioral problems and difficulties with sustained attention and memory than nonexposed children.
Researchers are not certain whether any effects of marijuana during pregnancy persist as a child grows; however, because some parts of the brain continue developing through adolescence, it's possible that certain kinds of problems will become more evident as a child matures.
Effects on the Brain
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 longtime 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.
As people age, they normally lose nerve cells in a region of the brain that is important for remembering events. Chronic exposure to THC may hasten the age-related loss of these nerve cells. In one study, researchers found that rats exposed to THC every day for eight months (about one-third of their life span) showed a loss of brain cells comparable to rats that were twice their 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.
Medicinal Uses
There has been much debate 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, manufactured into a pill that is taken by mouth, not smoked, 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 from 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.
