Understanding Medical Cannabis (Marijuana)

Author: Marisa Healy, BSN, RN
Content Contributor: Allyson Distel, MPH
Last Reviewed: April 15, 2024

What is marijuana?

Marijuana is made up of the dried leaves and flowers of a plant called Cannabis. In the U.S., Federal law does not allow the use of cannabis. But, many states have made cannabis use legal.

Many people think of marijuana or cannabis as a plant only used to get “high.” But compounds (parts) of the plant can be changed or taken out and that takes away the “high” feeling. We will point out the compounds found in cannabis and how they can be used to help with many cancer symptoms and some medication side effects.

Cannabis Plant Species

There are two main types (species) of plants used as medical marijuana: Sativa and Indica. Most cannabis is a hybrid (mix) of both Sativa and Indica. Each kind can affect people differently based on their body and how their body handles it, along with the terpenes made by certain strains (discussed below).

  • Sativa plants grow in moist areas and are tall and skinny with long, thin leaves. Sativa species were thought to be more uplifting and energizing.
  • Indica plants grow in arid (dry) areas and are a shorter, stubbier plant with wide leaves to take in moisture. Indica species were thought to be more calming, some are even sedating which means they cause sleepiness.

What are cannabinoids?

The cannabis plant has more than 110 chemical compounds called cannabinoids, with even more that we don’t know about yet. Out of the 110, 2 have been looked at for medical use: THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol). These chemicals have effects on the body like medicines do. They can affect the central nervous system and the immune system in a few ways:

  • THC is the part of cannabis that has effects that can lead to a “high” feeling. It has been found to help with pain, nausea, and insomnia.
  • CBD is the part of cannabis that has been found to help with anxiety, inflammation, and pain. It has no psychoactive (affecting the mind) effects.

The Balance of THC and CBD

Cannabis strains are grown to have different amounts of THC and CBD to meet the needs a person may have for cannabis. This is called the THC:CBD ratio. THC and CBD work better together than either does alone. These products fit into 3 groups:

  • THC dominant: These strains have less CBD and can cause a strong “high,” sleepiness, and anxiety. How high a person feels can vary based on your tolerance. For this reason, it is often told to start with a low dose and work your way up.
  • CBD dominant: These strains have less THC than CBD, letting you have a clear head and keep your normal roles & responsibilities. When there is more CBD than THC, you will likely not have any psychoactive change.

Balanced CBD and THC: These can have a slightly higher amount of either part but are more balanced than the strains listed above. When there is a similar amount of CBD and THC, the CBD will cancel much of the psychoactive effects of the THC compound.

How do cannabinoids work?

There are receptors in our body that make up the endocannabinoid system (ECS). This is one of the most widely spread receptor systems throughout our bodies. Everyone’s ECS is different. Our bodies naturally make “endocannabinoids” that work with the ECS receptors. The ECS system helps our body keep balance (called homeostasis). Cannabinoids that come from plants (like cannabis plants) are also able to work with these receptors.

The two major ECS receptors are CB1 and CB2 receptors.

  • CB1 receptors are mostly found in the nerve cells of the brain and spinal cord. It is these receptors that THC interacts with to cause its psychoactive effects or “high.”
    • CB1 receptors can also be found in the spleen, GI tract, reproductive and urinary systems, endocrine system, and white blood cells. The fact that these receptors are found in so many parts of the body explains why cannabinoids can be used for many things.
    • CB2 receptors are often found in the immune and hematopoietic (blood cell) systems. They are also found in the brain to a lesser degree than CB1 receptors.

What are terpenes?

Terpenes are compounds or essential oils found in many plants and some insects. They cause some of the taste and smell of the object. Terpenes bind to receptors like cannabinoids, causing certain results in the body, and can act on tissues and cells in the immune system. There are hundreds of terpenes, but a handful are more common.

Many labs that study cannabis, list terpene content on product labels, allowing you to choose a strain based on the terpenes it has. The more common cannabis terpenes are Myrcene, Terpinolene, Limonene, Humulene, Pinene, Linalool, and Caryophyllene.

Terpenes work together with cannabinoids. This is known as the “entourage effect.” Some studies have found that using one cannabinoid, without the entourage of compounds found in the cannabis strain it came from, leads to less benefits.

How is cannabis used in cancer care?

Cannabis products are most often used for symptom management in people with cancer. It may be used to help manage pain, nausea, anxiety, and insomnia, and can stimulate (rev up) the appetite when weight loss is a concern. Some compounds of cannabis are being studied to see if they can slow down or stop cancer cell growth. Research is needed to know how it works and which products and cancer types will have the best results.

How is cannabis taken?

Cannabis can be taken or used in its whole plant form (often the flowers or “buds” of the plant) or compounds taken from the plant (THC or CBD). It can be taken in 3 main ways:

  • Inhalation (through smoke or vapor).
  • Consumption (by mouth).
  • Topically (through creams, lotions, ointments, etc).

Different states have made different methods or products legal, so you may not have these options based on where you live.

Inhalation of Cannabis

Inhalation means breathing in. Cannabis can be smoked in a pipe, hookah, or rolled into a “joint” (rolled in cigarette paper) or “blunt” (rolled in tobacco paper). Cannabis can also be inhaled in vapor form – called vaporized. This is done using a vaporizer, which heats the product enough to release the cannabinoids but does not ignite or burn the product.

Many different types of vaporizers use cannabis forms, such as the bud of the plant, and an oil or wax/resin (also called shatter). These may be used by adding them to the vaporizer or may come in pre-filled cartridges that fit in the vaporizer.

Vaporization works quicker than oral methods – in as little as 1 to 15 minutes. It often lasts 1-3 hours, which is shorter than ingested (swallowed) methods. During vaporization, CBD and THC are inhaled into the lungs along with other compounds. This can be a concern, mostly for people with lung disease or cancers affecting the lungs.

Taking Cannabis by Mouth

There are a few ways to take cannabis by mouth, such as tinctures, capsules, oils, and edibles.

  • Tinctures are liquids that are mainly used sublingually, meaning it is placed under the tongue to sit for about 30 seconds. This lets it be quickly absorbed and can start working in 15-30 minutes. Sublingual cannabis tends to last about 2-4 hours in the body. A tincture (liquid form) can also be swallowed directly or placed in a liquid beverage, though this takes longer to work (30-90 minutes).
  • Oils can be used as a sublingual (under the tongue), can be swallowed, or taken in a capsule/softgel. CBD and THC oils often come in 3 types:
    • Full-spectrum– Has all the compounds found in the source product, such as THC, CBD, terpenes, and other cannabinoids.
    • Broad-spectrum– Has many of the compounds from the source plant, but THC is removed.
    • CBD isolate– Has only CBD with all other compounds removed.
  • Cannabis oils, tinctures, flower, or ingredients infused with cannabis (such as butter or vegetable oil) can be used to make foods or drinks that produce the effects of cannabis. These are called edibles. Consuming cannabis in this way will have an effect in about 30 to 90 minutes, but can last for 4 to 8 hours.

Using Topical Cannabis

Topical cannabis is made by heating the cannabis flower to activate the cannabinoids and making an extract from this. This can be made into a lotion, cream, or ointment. These can give pain relief to the area they are used on. The cannabinoids are not absorbed (taken in) to the bloodstream, so there is no risk of getting high. Topical cannabis works quickly – within 1 to 10 minutes and can last up to 5 hours.

Another “topical” method is transdermal, which means the cannabis is taken in by a patch that is placed on your skin. These compounds are absorbed into your bloodstream. THC is absorbed, so there is a risk of psychoactive effects. These are made as either THC alone or a balanced formula that has both THC and CBD.

How does cannabis from a dispensary differ from recreational marijuana?

A dispensary has trained staff to help you choose products. They can help you choose the right product and ratio of THC:CBD for your needs. Marijuana from a dispensary is regulated and labeled with ingredients and amounts so you know and are comfortable with what you are using. Recreational marijuana is not regulated. You cannot be sure what you are getting, if there are contaminants, or if it is safe.

What about the CBD products I see in the mall/grocery store/etc.?

CBD products found in stores and online are made from the hemp plant, which has less than 0.3% THC and will not cause any “high” effect. The main difference between hemp and marijuana is that hemp makes much less THC and does not have many of the other helpful compounds found in cannabis. For this reason, CBD oil from hemp may not have the same effects as CBD from cannabis.

When buying CBD oil from a cannabis dispensary, you will need to look at the THC content. The staff in a shop can help you find how much THC is best for your needs. Every person’s body is different, and you may need to try a few products before you find the best one for your needs.

How can I access cannabis?

Each state has its own laws and processes for getting access to medical cannabis. In a few states, cannabis is legal for all adults. In most states, you must have a health condition on that state’s list of conditions to get medical cannabis. If you have a condition that qualifies, you will need to get a medical marijuana card to visit a dispensary (the place cannabis products are sold), buy, and carry products. In some states, you are also able to grow small amounts of cannabis.

The first step is to visit a provider registered with your state who can suggest or certify you for medical cannabis use. In some states, this must be a doctor (MD or DO), while nurse practitioners (NPs) and physician’s assistants (PAs) can do so in other states. Since marijuana is federally illegal at this time, they cannot write a prescription for it as they do with other medications. Instead, the provider may recommend marijuana and can give you some guidance as to the type that might benefit you most. For instance, a person with breathing problems may be told not to use vaporized cannabis. You will then need to follow your state’s process for getting your medical card.

How can I learn more?

There are many resources for information about medical marijuana and CBD. Many states do not allow reciprocity, meaning you cannot use your card to buy medicinal cannabis outside of the state where you are registered. There may also be legal concerns with traveling across state lines with products.

If you are interested in learning more, the list below can help you get started in your research:

Birdsall, S. M., Birdsall, T. C., & Tims, L. A. (2016). The use of medical marijuana in cancer. Current oncology reports, 18(7), 40.

Cannabis and Cannabinoids (PDQ®)–Health Professional Version. (2024). [PdqCancerInfoSummary]. National Cancer Institute. https://www.cancer.gov/about-cancer/treatment/cam/hp/cannabis-pdq

Clark, C. S. (2018). Medical Cannabis: The oncology nurse's role in patient education about the effects of marijuana on cancer palliation. Clinical journal of oncology nursing, 22(1).

DeMarco, C. (2019). CBD oil and cancer: 9 things to know. Retrieved January 8, 2020, from https://www.mdanderson.org/publications/cancerwise/2019/09/cbd-oil-and-cancer--9-things-to-know.html

Kramer, J. L. (2015). Medical marijuana for cancer. CA: a cancer journal for clinicians, 65(2), 109-122.

National Conference of State Legislatures (2023). Retrieved January 8, 2020, from https://www.ncsl.org/research/health/state-medical-marijuana-laws.aspx#1Tuesday,

M. B., August 6, & 2019. (n.d.). What Is CBD Oil, and Can It Help People with Cancer?

Memorial Sloan Kettering Cancer Center (2021). Retrieved January 8, 2020, from https://www.mskcc.org/blog/what-cbd-oil-and-can-it-help-people

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