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Marijuana

Other common name(s): pot, grass, cannabis, weed, hemp, hash, marihuana, ganja

Scientific/medical name(s): Cannabis sativa

Description

Cannabis sativa is an annual plant that grows wild in warm and tropical climates throughout the world and is cultivated commercially. The leaves and buds of the plant have been used in herbal remedies for centuries. Scientists have identified 66 biologically active components, called cannabinoids, in marijuana. The most potent of these is thought to be the chemical delta-9-tetrahydrocannabinol, or THC, although other active substances are being studied.

Overview

The medical use of marijuana is limited because different strains of the plant contain different amounts of various compounds, which makes effects hard to predict. Medical researchers have isolated substances from the plant (cannabinoids) that can be used in precise doses alone and in combinations with other medicines to achieve more predictable effects. Certain cannabinoid drugs have been approved by the US Food and Drug Administration (FDA) to relieve nausea and vomiting and increase appetite in people with cancer and AIDS. Other marijuana extracts are still being tested.

How is it promoted for use?

THC and marijuana are promoted to relieve pain, control nausea and vomiting, and stimulate appetite in people with cancer and AIDS. Researchers also report that THC decreases pressure within the eyes, therefore reducing the severity of glaucoma.

Some supporters claim that marijuana has anti-bacterial properties, inhibits tumor growth, and enlarges the airways, which they believe can ease the severity of asthma attacks. Others claim that marijuana can be used to control seizures and muscle spasms in people who have epilepsy and spinal cord injuries.

As of 2012, there are reports online suggesting that marijuana oil or “hemp” oil can cure cancer, as well as diabetes, ulcers, arthritis, migraines, insomnia, infections, and many other diseases.

What does it involve?

Marijuana leaves, stems, seeds, and flowers are typically shredded and dried before use. In this crude form, marijuana is most commonly smoked in pipes, homemade cigarettes, or hollowed out cigars. It also may be mixed with foods and eaten, or made into tea. It can be made into a more concentrated, resinous form called hashish, or a sticky black liquid, hash oil. This is similar to what is now being called marijuana oil or hemp oil, which is made by using solvents and heat to remove the oil from the plant. Possessing or selling crude or raw marijuana is illegal under federal law in the United States. Whole or crude marijuana (including marijuana oil or hemp oil) is not approved by the FDA for any medical use.

There are chemically pure drugs based on marijuana compounds that have been approved in the US for medical use. The active ingredient THC has been available by prescription as dronabinol in pill or suppository form since 1985. A second drug, nabilone, is much like a cannabinoid. It is also a prescription drug, and is sometimes used when other drugs fail to reduce nausea and vomiting after chemotherapy. More recently, a chemically pure mixture of THC and cannabidiol (CBD) called Sativex® was made into a mouth spray. This prescription spray has been approved in Canada and parts of Europe to relieve pain linked to cancer as well as muscle spasms and pain from multiple sclerosis. It is not yet approved in the US as of early 2012, but it is being tested in clinical trials to see if it will help relieve cancer pain.

What is the history behind it?

Marijuana plants were made into fiber for rope and textiles, oil was taken from its seeds, and some cultures used it in religious rituals. It was described in Indian and Chinese medical texts more than 3,000 years ago. It was used to treat conditions such as beriberi, constipation, gout, malaria, rheumatism, and absent-mindedness, as well as depression, insomnia, vomiting, tetanus, and coughs. In the middle ages, herbalists used it externally to help muscle and joint pain.

In the mid-1800s, the plant was mentioned as a treatment for gonorrhea and angina (chest pains related to heart disease). It was also used to treat intestinal pain, cholera, epilepsy, strychnine poisoning, bronchitis, whooping cough, and asthma. In the US and Europe, marijuana extracts were prepared and sold for medicinal use as sedatives and pain relievers, to help appetite and sexual problems. By the early 20th century, it was noted that the extracts varied in their effects. Their actions in the body varied based on where the marijuana came from, how it was prepared, and how old it was. Other medicines became available that were more predictable and easier to use.

Things were already changing in the US in 1937, when marijuana use (even by doctors) was taxed. Then Congress passed a law in 1951 that classified marijuana as a narcotic drug. In 1970, marijuana was defined in a new law, the Controlled Substances Act, as a Schedule 1 drug -- a drug with no accepted medical use and with the potential for abuse. While marijuana is legal in many parts of Asia and the Middle East, it remains illegal in most Western countries.

In recent decades, marijuana has been the subject of extensive medical research using more advanced methods of testing as specific active compounds have been isolated. But political and legal controversies surrounding its status as an illegal substance, as well as concerns about potentially harmful side effects, have hampered the process of scientific inquiry in many countries, including the United States.

Despite this, researchers continue to study the compounds in marijuana for possible medical applications. Two prescription drugs based on marijuana compounds have been approved in the United States, and a third has been approved in Canada and Europe. The prescription drug dronabinol is an active ingredient of marijuana. It is used for patients with chemotherapy-related nausea and vomiting that does not respond to usual treatments, as well as for people with serious weight loss due to AIDS. Nabilone is another drug based on cannabinoids that is used for nausea and vomiting after chemotherapy. Other compounds are being tested for possible use as drugs.

What is the evidence?

There are many challenges in marijuana research. The whole plant contains many compounds, which have different actions in the human body. For example, studies show that THC can raise anxiety and cause paranoia, while cannabidiol (CBD) may reduce them. Components of the whole plant can have nearly opposite effects in the human brain, so that one compound can change the effects of another.

Different cultivars (strains or types) and even different crops of marijuana plants can have varying amounts of these compounds. This means that studies that use the whole plant may find different effects based on the strain of marijuana used. At least one researcher has shown a wide range of ratios between THC and CBD in marijuana that was seized by law enforcement agents in California. Marijuana seized more recently had much more THC and much less CBD by comparison to past seizures.

Another issue is that effects vary depending on how marijuana compounds enter the body. When taken by mouth, the THC is processed by the liver, which produces another psychoactive compound (a substance that acts on the brain and changes mood or consciousness). When marijuana smoke is inhaled, cannabinoids enter the bloodstream quickly. The extra psychoactive compound is produced in smaller amounts than when marijuana is taken by mouth.

And finally, the studies discussed below may have been done on marijuana extract (which would contain multiple compounds in variable amounts) or on one or more purified components of marijuana such as THC or CBD.

The mixture of CBD and THC has been approved in some other countries for cancer pain. It is being tested in clinical trials (on human volunteers) in the United States, and so far it is showing promise for helping people with cancer pain that is unrelieved by strong pain medicines. Studies have long shown that people who took marijuana extracts in clinical trials tended to need less pain medicine.

One review of studies published between 1975 and 1996 concluded that THC taken by mouth worked as well or better than older prescription drugs for reducing nausea associated with chemotherapy. It was not tested against the newer anti-nausea drugs, but 2 cannabinoid drugs are now approved for use in the US if other anti-nausea drugs don’t work.

Even though marijuana is widely thought to be helpful in people with glaucoma, the American College of Physicians noted in 2008 that large doses of cannabinoids are required to reduce eye pressure. This effect is short lived, and side effects, such as a reduction in blood supply to the optic nerve, may cancel out the benefit over the long term. Other medicines are generally more useful for people with glaucoma.

There is still concern that marijuana may cause toxic side effects in some people, and that the benefits of THC must be carefully weighed against its potential risks. Some people find the emotional and mental effects to be frightening, and a significant few have had temporary psychosis (loss of contact with reality) as a result of taking certain cannabinoids. Generally, however, the side effects of the purified extracts are mild and can be managed with careful dosing.

A number of reviewers have concluded that the scientific evidence does not support smoking marijuana as a medicine because of problems with dosing and the variable amounts of any one compound that might be delivered.

A 2006 study of people with advanced cancer and weight loss tested marijuana extract against low doses of THC and compared them to a placebo group. Over the 6-week period, all 3 groups reported improved appetite, so neither the THC nor marijuana extract helped more than placebo. However, doses used in this study were low and were not increased over time as is usually done with THC. A 2005 study in New York compared dronabinol and marijuana in people with HIV who had smoked marijuana previously. The researchers noted that both improved food intake in people who had severe weight loss due to their illness. Overall, several reviewers have concluded that cannabinoids are useful for improving appetite in patients with AIDS. The American College of Physicians also noted in its position paper that many studies show THC to be helpful in stimulating appetite in people with severe weight loss due to HIV.

A 2010 research review looked at studies using cannabinoids in people with multiple sclerosis (MS). The studies used a variety of medicines that contained THC and/or CBD, or a marijuana extract. People using the cannabinoids or extracts generally reported less severe problems with muscle spasms than those who got placebo. But when researchers measured the spasms, they couldn’t see much difference in the actual spastic movements between the drug and placebo. Some of them questioned whether the improvement was too small to measure objectively. One of the researchers noted that the patients also reported less pain, and another observed that spasms happened less often on the cannabinoids than on the placebo – either of which might explain why the patients felt better even though the improvement in spasms might have been small. Studies are still under way.

A small early study of CT-3, a substance related to delta-9-THC, looked at people with neuropathic pain (pain related to the nerves of the body). It tested CT-3 against a placebo, and found that patients reported lower pain levels 3 hours after receiving the CT-3 compared with placebo. Few other studies have been done on this compound, which is also called ajulemic acid.

The most in-depth investigation into the medical use of marijuana was authorized by the US Government in 1997. The Office of National Drug Control Policy commissioned the Institute of Medicine (IOM) to assess the potential health benefits and risks of marijuana. The IOM is an independent research body affiliated with the National Academy of Sciences. The IOM issued its final report in 1999 and offered several conclusions regarding marijuana's usefulness.

First, it found that scientific data indicate that cannabinoids, particularly THC, have some potential to relieve pain, control nausea and vomiting, and stimulate appetite. Cannabinoids probably affect control of movement and memory, but their effects on the immune system are unclear. It found that some of the effects of cannabinoids, such as reduced anxiety, sedation, and euphoria, may be helpful for certain patients and situations and distressing for others. Based on the many studies reviewed, researchers also found that smoking marijuana delivers harmful substances and may be an important risk factor in the development of lung diseases and certain types of cancer. The IOM stated that because marijuana contains a number of active compounds, it cannot be expected to provide precise effects unless the individual components are isolated.

More recently, scientists reported that THC and other cannabinoids such as CBD (cannabidiol) slow growth and/or cause death in certain types of cancer cells growing in laboratory dishes. Some animal studies also suggest certain cannabinoids may slow growth and reduce spread of some forms of cancer. However, these substances have not been tested in humans to find out if they can lower cancer risk. There is no available scientific evidence from controlled studies in humans that cannabinoids can cure or treat cancer.

Again, cannabinoid levels in marijuana are unpredictable and lower than doses used in most animal studies, so any benefit from this compound would require use of a purified and concentrated form. This is also true of marijuana oil or hemp oil, since purified oils contain roughly the same ratios of compounds as the plants from which they are made. Even though some proponents of marijuana oil recommend using Cannabis indica (rather than C. sativa) for its higher cannabidiol levels and lower THC levels, the levels cannot be considered consistent or predictable.

Are there any possible problems or complications?

This substance may not have been thoroughly tested to find out how it interacts with medicines, foods, herbs, or supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Because of these limitations, any information on ill effects and interactions below should be considered incomplete.

Smoking or eating whole marijuana can cause a number of mental and emotional effects, including feelings of euphoria, short-term memory loss, difficulty in completing complex tasks, changes in the perception of time and space, sleepiness, anxiety, confusion, and inability to concentrate. A small but significant percentage of people in medical studies didn’t like the mental effects and withdrew from studies because of them. In studies, cannabinoids have been linked with effects such as depression, paranoia, and hallucinations. People who are prone to mental illness may have more serious mental and emotional effects from marijuana use.

Physical side effects include low blood pressure, fast heartbeat, dizziness, slow reaction time, and heart palpitations. Instances of serious heart problems are very rare.

Many researchers agree that marijuana smoke contains known carcinogens, or chemicals that can cause cancer much like those in tobacco smoke. Studies have shown changes in the linings of the breathing passages in marijuana smokers. But results of epidemiologic studies of marijuana and cancer risk have been inconsistent, and most recent epidemiologic studies have not found a substantial effect on cancer risk. It’s possible that some of these differences are due to the fact that most marijuana smokers don’t smoke as much or as often as tobacco smokers. Effects might be more evident in heavy marijuana smokers. Some researchers also caution that these studies are difficult to conduct, as some people may not admit to illegal habits such as smoking marijuana, and that negative results should not be interpreted as convincing evidence of safety. They caution that smoking marijuana may cause lung disease and increase the risk of cancer of the lungs, mouth, and tongue.

There is debate on whether marijuana is truly addictive. Some heavy smokers of marijuana show signs of dependence on the drug, meaning that they continue to use it even in the face of bad consequences.

Frequent users may have withdrawal symptoms if they stop it suddenly. Restlessness, irritability, mild agitation, sleep disturbances, nausea and cramping have been observed. Withdrawal symptoms have also been demonstrated in animal studies.

Women who are pregnant or breastfeeding should not use marijuana.

Marijuana overdoses do not cause death, but may cause mental impairment and distressing emotional states, such as paranoia, hallucinations, and disconnection from reality. Overdose can also cause fast or disturbed heart rhythm, sleepiness, clumsiness, dry mouth, dizziness, and low blood pressure.

Although it is rare, European doctors have reported severe shutdown of blood circulation to the arms or legs in young people who smoked marijuana. In some cases, it was so severe that amputation was required. There is some debate as to whether smoking cigarettes, contaminated marijuana, or using other drugs may be part of this problem.

Marijuana may also serve as a trigger for a heart attack on rare occasions, usually within an hour after smoking. Allergic reactions, some severe, have been reported.

Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.

Drugs derived from marijuana also have side effects

Dronabinol and nabilone, prescription drug forms of THC, also can cause complications. People with heart problems may have trouble with increased heart rate, decreased blood pressure, and fainting. These drugs can cause mood changes or a feeling of being “high” that some people find uncomfortable. They can also worsen depression, mania, or other mental illness. The drugs may increase some effects of sedatives, sleeping pills, or alcohol, such as sleepiness and poor coordination. Dizziness, dry mouth, and trouble with recent memory are side effects even with controlled doses of THC and other purified components like it.

Driving, operating machinery, or hazardous activities that require clear thinking and good coordination are not recommended until the effects of THC-based drugs are known. People taking these drugs should be under the supervision of a responsible adult at all times when they start taking the medicine and after any dose changes.

Like marijuana, these drugs should not be used if a woman is breastfeeding because they can be concentrated in breast milk and passed to the baby. THC drugs are not recommended during pregnancy. People who have had emotional illnesses, paranoia, or hallucinations may become worse when taking THC or marijuana-based drugs.

Older patients may have more problems with side effects and are usually started on lower doses.

To learn more

More information from your American Cancer Society

The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).

Complementary treatments and herbal medicines

Complementary and Alternative Methods and Cancer

Dietary Supplements: What Is Safe?

Placebo Effect

The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management

Finding out about new ways to treat and prevent cancer

Learning About New Ways to Treat Cancer

Learning About New Ways to Prevent Cancer

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Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.


Last Medical Review: 04/02/2012
Last Revised: 07/13/2012