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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 U.S. 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).
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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: 11/01/2008
Last Revised: 11/01/2008
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