Marijuana, hemp, and cannabis are common names for plants of the genus Cannabis. The term "hemp" is used for Cannabis plants that are grown for nondrug use, such as Cannabis sativa. Cannabis indica has poor fiber quality and is used to make drugs for recreation and medicine. The major differences between the two are appearance and the amount of delta-9-tetrahydrocannabinol (THC), the active ingredient of marijuana.
Cannabis sativa is widely used for recreation. It has been inhaled or taken by mouth to produce a feeling of relaxation or well-being. The plant has been studied as a potential treatment for many conditions, including chronic skin disorders, cancer-related weakness and weight loss, chronic pain, Huntington's disease, sleep disorders, eye disease, multiple sclerosis, and schizophrenia. The most significant benefits have been seen in the treatment of chronic pain and multiple sclerosis. Marijuana may help reduce eye pressure in people who have glaucoma.
The most commonly studied ingredients in marijuana are THC and cannabidiol (CBD). Research has looked at these compounds both alone and in combination. Commercially available products include dronabinol (Marinol®), nabilone (Cesamet®), THC, and CBD (Sativex®).
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These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Marijuana has been studied for the treatment of chronic pain. It has been used in people whose pain did not respond to other drugs such as narcotics. Cannabis-based products like Sativex® are used to treat different types of pain, such as pain from cancer or multiple sclerosis. It is approved in Canada and many parts of Europe. In the United States, it is being studied in people who have cancer-related pain. Other cannabis-based products, such as the U.S. Food and Drug Administration (FDA)-approved dronabinol (Marinol®), are also being studied.
Marijuana has been studied for the relief of multiple sclerosis symptoms, such as nerve pain, muscle spasms, and urinary disorders. The active ingredients have effects on the central nervous system and immune cells.
Amyotrophic lateral sclerosis (nerve cell disease)
Current studies show that THC may lack benefit in people who have amyotrophic lateral sclerosis. More research is needed.
Current studies show that cannabis-based therapy may lack benefit on weight loss and anorexia related to cancer. Early studies suggested that marijuana may improve appetite in people who have cystic fibrosis (mucus buildup in the organs) and AIDS. More research is needed.
Atopic dermatitis (itchy, scaly skin rashes)
Hemp seed oil may help reduce symptoms of atopic dermatitis, a chronic skin disorder that causes itchy, scaly rashes. This benefit is believed to come from the fatty acids in hemp seed oil. Further research is needed.
Marijuana has been studied for potential benefit in people with acute brain injury. However, more research is needed before conclusions can be made.
Chemotherapy side effects
Studies suggest that marijuana may help reduce nausea and vomiting in people undergoing chemotherapy. However, it may cause side effects such as sleepiness and changes in mood. One review suggests that marijuana may cause more side effects in children undergoing chemotherapy than other therapies. However, the effect of cannabis alone is unclear, and further research is needed.
Early studies suggest that marijuana may benefit weight gain and behavior in people who have dementia. More research is needed before conclusions can be made.
In patients with eating disorders THC had a lack of effect on weight, caloric intake, and psychiatric assessment. Further research is required.
Early studies suggest that marijuana taken with antiseizure drugs may lower seizure risk in people with epilepsy. However, the evidence is limited. More research is needed on whether marijuana may be effective in treating epilepsy.
Glaucoma (high eye pressure)
People who have glaucoma have high pressure in the eye, which may lead to optic nerve damage and vision loss. Some studies suggest that THC may lower eye pressure, while CBD may lack benefit or actually increase pressure. More research is needed to understand the possible role of marijuana in glaucoma treatment.
Huntington's disease (nerve cell death in brain)
Symptoms of Huntington's disease include impaired brain function and jerky body movements. Early research suggests that CBD may lack effect on movement problems caused by Huntington's, although the marijuana-based drug nabilone may have benefits. More studies are needed in this area.
Marijuana has been studied in the treatment of symptoms of nerve and muscle disorders. Researchers looked for possible benefits on appetite, saliva production, mood, muscle health, and sleep. More research is needed before conclusions can be made.
Quality of life
There is some controversy over the use of marijuana in people who have cancer or other long-term illnesses. It has been studied for increasing appetite, treating stomach problems, improving mood and sleep, and reducing pain. More research is needed before conclusions can be made.
Limited research suggests that Sativex® may reduce pain and improve sleep quality in people who have rheumatoid arthritis. More research is needed.
Early research suggests that CBD may lack effect in people who have schizophrenia. Other research reports that cannabis users may have better brain function than nonusers. However, long-term use of cannabis has been linked to a higher risk of psychiatric problems. These include bipolar disorder, anxiety, suicidal thoughts, depression, delusions, hallucinations, aggression, and lack of motivation or energy. More research is needed.
Limited research suggests that CBD may help people who have problems sleeping. However, more studies are needed before conclusions can be made.
Tourette's syndrome (brain disorder causing tics)
Some research reports that marijuana may improve some symptoms of Tourette's syndrome. However, significant benefit over placebo is lacking for tics and other symptoms. More research is needed in this area.