Medical marijuana

Citation metadata

Author: Teresa G. Odle
Editor: Jacqueline L. Longe
Date: Apr. 4, 2018
Publisher: Gale, a Cengage Company
Document Type: Topic overview
Length: 1,303 words

Document controls

Main content

Full Text: 


Medical marijuana is the use of a marijuana plant or basic extracts of the plant to treat certain conditions and disease symptoms.


Cannabinoids in medical marijuana are used to manage many conditions and symptoms of diseases or conditions, including:

  • reducing nausea, especially from chemotherapy drugs
  • lessening pain
  • helping with muscle control problems
  • managing seizures

Researchers continue to explore the 100 cannabinoids in marijuana and possible uses in medicine. As of early 2018, the most common conditions approved for medical marijuana use in various states included:

  • glaucoma
  • cancer
  • epilepsy and seizures
  • chronic, severe pain
  • severe nausea
  • appetite improvement for weight gain (wasting syndrome)
  • severe muscle spasms
  • multiple sclerosis

In addition, medical marijuana has been used to help people with some heart and lung diseases, Parkinson's disease, dementia, and some mental health conditions. There is research suggesting that medical marijuana could help lower use of prescription opioids and deaths from opioid overdose. In addition, it is possible that prescribing marijuana for patients with pain could reduce the dose of opioids required to control the pain. However, there was not sufficient evidence as of spring 2017 to prove the effects of legalizing medical marijuana on the opioid epidemic, and research continues.


Medical marijuana is a growing but controversial treatment. Also called medical cannabis, the treatment comes from the Cannabis sativa plant with origins in the ancient world. The ingredient in marijuana considered mind altering is THC (delta-9-tetrahydrocannibiol). Medical use of cannabis is distinct from recreational use. Medical marijuana refers to use of cannabis, THC, and other cannabinoids as recommended by a physician or herbal therapist. In states that have legalized medical marijuana, the patient must present a written statement from a physician saying the marijuana is to treat medical conditions or manage side effects. The U.S. Federal Drug Administration (FDA) had not yet approved medical marijuana as a drug treatment by 2018. However, the FDA had approved two medications that include cannabinoid chemicals in their pills.


Cannabis might have been used for medical purposes as early as 400 AD. In the nineteenth and twentieth centuries, Americans often used cannabis medically. In 1937, an act was passed to regulate use of medical marijuana and the treatment was dropped from the official listing of pharmacy products in 1942. In the 1950s, legal penalties for possessing marijuana increased. The Controlled Substances Act of 1970 further prohibited its use, classifying the drug under Schedule I, which includes drugs such as heroin and ecstasy that have high likelihood of abuse, no accepted medical use, and concerns about safety for its use, even under medical supervision. As of 2018, marijuana still was classified in the United States as a Schedule I drug.

More than half of the states in the United States had made medical marijuana legal by early 2018 and some had legalized or decriminalized recreational use of the drug. Despite state laws approving use of medical marijuana, it still was considered illegal as of 2018 by the federal government. In 2016, an estimated 22.2 million Americans had reported using cannabis in the previous 30 days. Canada first legalized limited use of medical marijuana in 2000. In 2013, legislation included developing a list of licensed providers to grow marijuana. The country has listed specific approved uses of the drug. Therapy with medical marijuana surged in popularity in Canada in 2017.

Recommended dosage

Medical marijuana can be smoked, vaporized, eaten, or taken as a liquid extract. New products for medical use continue to be developed, such as oil and various types of inhaled substances with cannabis. Two medications approved by the FDA that contain cannabinoids are dronabinol (Marinol) and nabilone (Cesamet). These substances can be made and managed to control dose, and should be labeled to explain the amount of the cannabinoid included. For general medical marijuana products, Health Canada suggests limiting cannabis to no more than 3 grams per day and that patients wait between inhalations or infused products. This gives the patient time to monitor effects and lessen chance of overdosing. Medical marijuana typically is taken daily and specific dose depends on the product, reason for use, and method in which the drug is taken, such as by mouth, inhaled, or rubbed on the skin.

Side effects

Most of the information on side effects of medical marijuana has been adapted from reports of recreational users. Some side effects of medical marijuana use have been reported, including:

  • fast or irregular heartbeat
  • drowsiness and dizziness
  • slower reaction times than normal
  • problems coordinating movement
  • short-term memory loss
  • strong feelings of happiness
  • confusion and difficulty concentration
  • impaired judgment


Research continues on possible interactions between medical marijuana and prescription medications. Early research on dronabinol showed no concerning drug reactions. Still, it is important for those taking medical marijuana to inform all doctors of its use so the doctor can be certain the marijuana does not lessen the effects of other medications and risk of possible harmful interactions.

Research and general acceptance

Studying the health effects of medical marijuana presents special challenges, including legal restrictions and inconsistent concentrations of cannabinoid chemicals extracted from plants. Studies eventually should lead to better understanding of how to use medical marijuana as safely and effectively as possible.

A 2017 report from the National Academy of Sciences stated there was substantial evidence that cannabis is effective for treating chronic pain in adults and for helping people with multiple sclerosis or similar diseases to ease spasticity. Strong evidence also supported use of oral cannabinoids to ease nausea and vomiting in patients undergoing chemotherapy. There was some evidence in the report that medical marijuana could improve sleep in people who had trouble sleeping because of problems such as apnea or conditions causing chronic pain. Slight evidence also was found that medical marijuana could increase appetite in people with HIV/AIDS, improve symptoms of Tourette's syndrome, and relieve symptoms of social anxiety and posttraumatic stress disorder. Many other findings were not conclusive until more research is completed.

Parental concerns

Medical marijuana might be allowed or recommended for children with conditions such as epilepsy and only when the child is under close medical supervision. Research on marijuana side effects, precautions, and effectiveness typically study adults only. Parents should use caution when considering medical marijuana for treatment. Parents also should be aware of all medical marijuana laws and the potential legal and medical risks of giving medical marijuana products to their children. The lack of research on how medical marijuana affects health should lead parents to ask many questions of a doctor and careful monitoring of their child for side effects.

Sidebar: HideShow

Key Terms

Collapse or blocking of the airway during sleep that can affect breathing and cause loud snoring. Also called obstructive sleep apnea.
Types of chemicals in medical marijuana.
Ongoing, or long lasting, diseases and conditions.
To remove penalties or legal restrictions against an act.
A class of drugs that act on the nervous system and can ease pain. Opioids are prone to abuse and fatal overdose in many patients.
The condition in which muscles stay contracted, or stiff and tight.
Wasting syndrome
Too much weight loss, usually from loss of appetite, that can lead to problems with nutrition and muscle strength.


Stopping use of medical marijuana could lead to some withdrawal symptoms, but the symptoms are not considered severe and do not last long. Withdrawal symptoms include restlessness, mild agitation, nausea, and trouble sleeping. Several research studies suggest that marijuana smoke adds to risk of respiratory diseases.

In general, medical marijuana had little regulation and consistency regarding quality, labeling, packaging, and recommendations for use as of 2017. Medical marijuana involves legal as well as medical issues. The debate over whether medical marijuana should be legalized is affected by political and public opinion. Anyone considering use of medical marijuana should consult a physician and remain updated on new research about effectiveness and safety of medical marijuana, as well as legal issues.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

Source Citation

Source Citation   (MLA 8th Edition)
Odle, Teresa G. "Medical marijuana." The Gale Encyclopedia of Medicine, edited by Jacqueline L. Longe, 5th ed., Gale, 2015. Gale Health and Wellness, Accessed 14 Dec. 2019.

Gale Document Number: GALE|RERUXD302166506