Marijuana

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

Scientific/medical name(s): Cannabis sativa, delta-9-tetrahydrocannabinol (THC)

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 ingredients, 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 tested.

Overview

The cannabinoid drug THC has been approved by the US Food and Drug Administration (FDA) for use in relieving nausea and vomiting and increasing appetite in people with cancer and AIDS. Testing of other marijuana extracts is still in the early stages. Results are mixed in studies of marijuana use for muscle tremors and spasticity in people with multiple sclerosis or Parkinson’s disease.

How is it promoted for use?

THC is 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 may 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.

What does it involve?

THC has been available by prescription (as dronabinol) in pill or suppository form since 1985. Several pharmaceutical companies are also developing a form of THC that would be delivered through an inhaler. Some research studies use a liquid cannabis-based extract that is sprayed in the mouth to deliver marijuana compounds.

In raw form, marijuana is most commonly smoked in pipes or homemade cigarettes. It is also eaten directly or mixed with foods. Raw marijuana is illegal in the United States and is not approved by the FDA for medical uses.

What is the history behind it?

Marijuana has been described in Indian and Chinese medical texts for more than 3,000 years. 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 relieve 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. Marijuana is legal in many parts of Asia and the Middle East but illegal in most Western countries.

In the last few years, marijuana has been the subject of extensive medical research. However, 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 marijuana’s potential medical applications.

The prescription drug dronabinol is made from an active ingredient of marijuana. It is available for patients with chemotherapy-related nausea and vomiting that does not respond to usual treatments. It is also used for people with AIDS and severe weight loss, sometimes called wasting.

What is the evidence?

Much of the research on marijuana has been centered on cannabinoids, the best known active ingredients in marijuana, and THC, the cannabinoid thought to be the most potent. Marijuana and its extracts have been studied for their effects on nausea and vomiting related to chemotherapy, appetite, glaucoma, neuropathic pain, and spasticity in patients with multiple sclerosis. Research findings have been mixed.

One review of studies published between 1975 and 1996 concluded that oral THC is as effective, or more effective, than commonly used prescription drugs for reducing nausea associated with chemotherapy. The reviewers also concluded that cannabinoids may be useful at low doses to improve appetite in patients with AIDS. They found that THC reduces eye pressure in people who have glaucoma. None of the studies, however, showed that THC or other ingredients in marijuana addressed the underlying causes of glaucoma. They reported that marijuana may cause toxic side effects, and the benefits of THC must be carefully weighed against its potential risks. They concluded that the evidence did not support smoking marijuana as a medication and that additional research was needed.

Further research into marijuana’s benefit for nausea and vomiting has had conflicting results. A review study suggested that cannabinoids did not work better than standard treatment when used with chemotherapy known to produce severe vomiting.

Another comprehensive review of marijuana studies found there was not enough persuasive evidence to recommend marijuana as a treatment for nausea. However, a more recent study concluded that specific chemicals in marijuana, or synthetic copies of those chemicals, may prove helpful to some patients with certain illnesses or symptoms, including nausea.

A 2006 study of people with advanced cancer and weight loss found that neither cannabis extract nor low doses of THC improved appetite significantly better than placebo. Over the 6-week period, all 3 groups reported improved appetite. 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.

A 2004 study looked at people with multiple sclerosis (MS) using cannabis-based liquid extract. This liquid extract contained both THC and cannabidiol, which has different activity from THC. The patients receiving the extract reported less spasticity than those on placebo. In contrast, a small study that looked at arm tremors in people with MS compared the liquid marijuana extract with placebo. It found no measurable difference in tremor between people getting the extract and those on placebo.

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.

The most in-depth investigation into the medical use of marijuana was authorized by the U.S. 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 undesirable 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 cannabidiol, one of the chemicals found in marijuana, slows growth of breast cancer cells growing in laboratory dishes. However, this substance has not been tested in humans or even in animals that have cancer yet. Cannabidiol levels in marijuana are low, so any benefit from this compound would require use of a purified and concentrated form.

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 raw marijuana can cause a number of 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. In studies, cannabinoids have been linked with dizziness, depression, paranoia, and hallucinations. Other side effects include low blood pressure, rapid heart beat, and heart palpitations. Instances of death are rare. A review of studies looked at cannabinoid use in chemotherapy patients and found that one in eleven would stop using it because of side effects.

Many researchers agree that marijuana contains known carcinogens, or chemicals that can cause cancer. 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. However, some researchers caution that these studies are difficult to conduct, as some people may not be truthful about illegal habits such as smoking marijuana, and that these negative results should not be interpreted as convincing evidence of safety. They caution that smoking marijuana may decrease reproductive function, cause lung disease, and increase the risk of cancer of the lungs, mouth, and tongue. It may also suppress the body's immune system and increase the risk of leukemia in children whose mothers smoke marijuana during pregnancy. Women who are pregnant or breastfeeding should not use marijuana.

The symptoms of a marijuana overdose include nausea, vomiting, hacking cough, disturbances to heart rhythms, and numbness in the limbs. Chronic use can also lead to laryngitis, bronchitis, and general apathy. With chronic use, the ability to learn and remember new information may become impaired.

Although it is rare, severe shutdown of blood circulation to the arms or legs has been reported in young people who smoked marijuana. In some cases, it was so severe that amputation was required. 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.

Dronabinol, the prescription drug form of THC, also can cause complications. People with heart problems may have trouble with increased heart rate, decreased blood pressure, and fainting. Dronabinol can cause mood changes or a feeling of being "high" that is uncomfortable for some people. It can also worsen depression, mania, or other mental illness, and it may increase some effects of sedatives, sleeping pills, or alcohol, such as sleepiness and poor coordination.

Driving, operating machinery, or engaging in hazardous activities that require clear thinking and good coordination are not recommended until dronabinol’s effects are known. People taking dronabinol should be under the supervision of a responsible adult at all times when they start taking the medication and after any dose adjustments.

Like marijuana, dronabinol should not be used during breast-feeding because the drug is concentrated in breast milk and is passed to the baby. It is not recommended during pregnancy. People who have had emotional illnesses, paranoia, or hallucinations may become worse when taking dronabinol or marijuana.

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

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

Additional resources

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).

Guidelines for Using Complementary and Alternative Therapies

Dietary Supplements: How to Know What Is Safe

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

Complementary and Alternative Methods for Cancer Management

Placebo Effect

Learning About New Ways to Treat Cancer

Learning About New Ways to Prevent Cancer

References

Barsky SH, Roth MD, Kleerup EC, Simmons M, Tashkin DP. Histopathologic and molecular alterations in bronchial epithelium in habitual smokers of marijuana, cocaine, and/or tobacco. J Natl Cancer Inst. 1998;90:1198-1205.

Bolla KI, Eldreth DA, Matochik JA, Cadet JL. Neural substrates of faulty decision-making in abstinent marijuana users. Neuroimage. 2005;26:480-492.

Cannabis-In-Cachexia-Study-Group, Strasser F, Luftner D, Possinger K, et al. Comparison of orally administered cannabis extract and delta-9-tetrahydrocannabinol in treating patients with cancer-related anorexia-cachexia syndrome: a multicenter, phase III, randomized, double-blind, placebo-controlled clinical trial from the Cannabis-In-Cachexia-Study-Group. J Clin Onc. 2006;24:3394-3400.

Disdier P, Granel B, Serratrice J, et al. Cannabis arteritis revisited--ten new case reports. Angiology. 2001;52:1-5.

DuPont RL. Examining the debate on the use of medical marijuana users. Proc Assoc Am Physicians. 1999;111:166-172.

Fox P, Bain PG, Glickman S, Carroll C, Zajicek J. The effect of cannabis on tremor in patients with multiple sclerosis. Neurology. 2004;62:1105-1109.

Gruenwald J. PDR for Herbal Medicines. 3rd ed. Montvale, NJ: Thomson PDR; 2004.

Haney M, Rabkin J, Gunderson E, Foltin RW. Dronabinol and marijuana in HIV(+) marijuana smokers: acute effects on caloric intake and mood. Psychopharmacology. (Berl). 2005;181:170-178.

Hashibe M, Morgenstern H, Cui Y, et al. Marijuana use and the risk of lung and upper aerodigestive tract cancers: results of a population-based case-control study. Cancer Epidemiol Biomarkers Prev. 2006;15:1829-1834

Joy JE, Watson SJ Jr, Benson JA Jr. eds. Marijuana and Medicine: Assessing the Science Base. Washington, DC: National Academy Press; 1999.

Kalb C. No green light yet: a long-awaited report supports medical marijuana. So now what? Newsweek. 1999;133:35.

Karst M, Salim K, Burstein S, et al. Analgesic effect of the synthetic cannabinoid CT-3 on chronic neuropathic pain: a randomized controlled trial. JAMA. 2003;290:1757-1762.

Marijuana use in supportive care for cancer patients. National Cancer Institute Web site. Accessed at www.cancer.gov/cancertopics/factsheet/Support/marijuana on June 6, 2008.

McAllister SD, Christian RT, Horowitz MP, Garcia A, Desprez PY. Cannabidiol as a novel inhibitor of Id-1 gene expression in aggressive breast cancer cells. Mol Cancer Ther. 2007;6:2921–2927.

Mehra R, Moore BA, Crothers K, Tetrault J, Fiellin DA. The association between marijuana smoking and lung cancer: a systematic review. Arch Intern Med. 2006;166:1359-1367.

Mittleman MA, Lewis RA, Maclure M, Sherwood JB, Muller JE. Triggering myocardial infarction by marijuana. Circulation. 2001;103:2805-2809.

Nahas G, Latour C. The human toxicity of marijuana. Med J Aust. 1992;156:495-497.

Schwartz RH, Voth EA, Sheridan MJ. Marijuana to prevent nausea and vomiting in cancer patients: a survey of clinical oncologists. South Med J. 1997;90:167-172.

Smigel K. Cancer problems lead list for potential marijuana research studies. J Natl Cancer Inst. 1997;89:1255.

Tramér MR, Carroll D, Campbell FA, et al. Cannabinoids for control of chemotherapy induced nausea and vomiting: quantitative systematic review. BMJ. 2001;323:16-21.

Voth EA, Schwartz RH. Medicinal applications of delta-9-tetrahydrocannabinol and marijuana. Ann Intern Med. 1997;126:791-798.

Wade DT, Makela P, Robson P, House H, Bateman C. Do cannabis-based medicinal extracts have general or specific effects on symptoms in multiple sclerosis? A double-blind, randomized, placebo-controlled study on 160 patients. Mult Scler. 2004;10:434-441.

Woolridge E, Barton S, Samuel J, et al. Cannabis use in HIV for pain and other medical symptoms. J Pain Symptom Manage. 2005;29:358-367.

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.