Medical Marijuana

Marijuana can have a range of effects on the brain. It can affect mood, appetite, behavior, and pain sensation. Because of this, some have turned to marijuana to help manage certain medical issues. Not all uses of marijuana are fully supported by research but interest is growing.

Cannabinoids at Work

The effect of marijuana is caused by chemicals called cannabinoids. The most common are delta-9 tetrahydrocannabinol (THC) and cannabidiol (CBD), but there are hundreds more. How much of each type of chemical is in a plant will determine the effects it has. All the chemicals have a direct effect on the brain.

THC causes the "high" or euphoria associated with marijuana. Medical strands of marijuana may have low levels of THC. This means there is no or little feeling of "high" while still having medical benefits.

Medical marijuana may be available as:

  • Herbal—dried out buds or leaves that are smoked, vaporized, or eaten
  • Synthetic—created in a lab
  • Extracts—concentrated active ingredients can be used in pills or oils

Potential Uses for Medical Marijuana

Research needs to be done to support most medical use of marijuana. However, marijuana has been used to help manage the following:

  • Chronic or severe pain
  • Muscle spasms or stiffness
  • Glaucoma
  • Complications of HIV and AIDS
  • Epilepsy
  • Severe nausea and vomiting associated with chronic diseases or their treatments
  • Muscle wasting or severe weight loss associated with chronic diseases or their treatments
  • Manage seizures in children with certain types of epilepsy

Marijuana is often not the first choice for treatment. In many cases, it may be used only when other treatments have failed. It may also be an option if other treatment choices have unwanted side effects.

Side Effects of Marijuana Use

Marijuana, like any drug, can have side effects. Some can be serious. They can also vary between types of marijuana. Like any other drug, side effects will also depend on dose and how your body reacts to it.

Minor side effects may include:

  • Cognitive symptoms, such as confusion, and problems with memory and concentration
  • Slowed thinking and reaction time
  • Lightheadedness
  • Fatigue and drowsiness
  • Dry mouth
  • Vertigo—a sensation of spinning when standing still
  • Heart palpitations
  • Headache

Serious side effects may include:

  • Severe or recurrent nausea and vomiting
  • Low achievement and lack of motivation
  • Dependency—increased tolerance and strong desire to use marijuana
  • Chronic bronchitis (and other tobacco-associated side effects)—if smoked
  • Irregular heart rhythm, which can lead to a heart attack or cardiac arrest
  • Development of mental illnesses, such as depression, anxiety disorders, bipolar disorder, schizophrenia, and psychosis
  • Suicidal thoughts or actions

Marijuana can also cause problem in pregnant women. It is linked with low birthweight, premature birth, and other complications for mother and baby. For this reason it is not recommended in women who are pregnant or planning to become pregnant.

Children and adolescents have rapidly growing brains. This makes them more vulnerable to the effects of any drug, even those given by a doctor. There is not enough research to know the exact effect of marijuana on younger brains. It is often only considered for extreme health concerns like uncontrolled seizures.

Where to Start

Talk with your medical team about your options. Marijuana can interfere with your treatment and other drugs. It is important to talk to your doctor before taking any new drugs. There may also be other, better understood treatments for your health issue.

Only get your medical marijuana from professional sources. This will make sure the marijuana is of high quality and proper dose. They will also have different strains to better meet your needs.

Know the Laws

Laws can vary. Check with the laws in your area for medical marijuana. Even if you have a prescription, there may still be some restrictions.


American Cannabis Nurses Association
US Food & Drug Administration


Cannabis Canada


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Medical use of cannabinoids. EBSCO DynaMed website. Available at: http://www.dynamed... . Updated January 11, 2017. Accessed April 6, 2017.
Epilepsy in children. EBSCO DynaMed Plus website. Available at: . Updated March 22, 2018. Accessed February 18, 2019.
Last reviewed February 2019 by EBSCO Medical Review Board Daniel A. Ostrovsky, MD
Last Updated: 02/12/2019

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