What You Need to Know About Medical Cannabis

Are proponents or detractors just blowing smoke?

cannibis

Medically reviewed in March 2022

Updated on March 25, 2022

Depending on whom you talk to, medical cannabis (also known as medical marijuana) is either a panacea for everything from cancer to chronic pain to epilepsy or a dangerous and illegal drug with no place in medicine.

On the one hand, evidence suggests that legal cannabis could replace alternative treatments and save the government big money on healthcare bills.

Research published in 2016 and 2017 in Health Affairs found that Medicaid and Medicare Part D spending decreased by millions of dollars in states where medical cannabis was legal. The researchers found that prescriptions for drugs used to treat anxiety, depression, nausea, pain, psychosis, seizures, and sleep disorders also declined in states with medical cannabis laws. They estimated that Medicare could have saved over $1 billion in 2014 if all states had such laws.

Data like that, plus additional studies, suggest that cannabis has a real effect on people’s health. But can it really treat so many conditions? The answer: yes, no, and maybe. Read on to find out more about we know, what we don’t, and why it’s complicated.

Cannabis’ complex legal status 
First of all, cannabis’ legal status is complicated, and that affects how easily it can be studied. As of February 2022, 37 states, four territories, and the District of Columbia allow medical cannabis. Additionally, 18 states, 2 territories, and the District of Colombia allow for the regulated recreational use of cannabis.

But federally, cannabis is classified as a Schedule I drug under the Controlled Substances Act, along with drugs such as mescaline and MDMA (ecstasy). That means the federal government has found it to have a high potential for abuse, has no medical use, and is unsafe. Products that contain either of cannabis’ two main ingredients, delta-9-tetrahydrocannabinol (THC) or cannabidiol (CBD), aren’t legally sellable as dietary supplements.

The status of cannabis as a Schedule I drug makes it hard to get funding for research into its medical benefits, says Keith Roach, MD, associate professor in clinical medicine in the division of general medicine at Weill Cornell Medical College and New York Presbyterian Hospital.

“I think it should be reclassified because there’s potential for marijuana to be used in other conditions,” says Dr. Roach. “Saying it has no medical validity is a mistake. Let’s study it.”

Roach says the future of medical marijuana research “depends entirely on the federal government and what they choose to do. Right now, it’s very difficult for researchers to do any kind of good research.”

Elements of cannabis
In addition, cannabis isn’t just one thing—as with any plant, it contains hundreds of compounds with potential health effects, including some very important ones called cannabinoids. The two most common cannabinoids are THC, which is responsible for the “high” that cannabis causes, and CBD, which does not have psychoactive properties.

In November 2017, the World Health Organization (WHO) published a report stating that CBD in its pure form is safe, with little potential for substance abuse and no evidence of harm to public health. The U.S. Drug Enforcement Administration classifies CBD as a Schedule V controlled substance, a category that also includes cough syrups.

CBD is not risk-free—it can interact with other drugs and may caused vomiting, diarrhea, sleepiness, or liver abnormalities. But it also has potential health benefits (read on to learn more). And THC has important medical uses as well.

In fact, the effectiveness of certain compounds found in cannabis are no longer in question, says Roach. “But it’s still controversial because marijuana itself has a lot of different substances in it. We try to isolate one substance and say ‘This is what’s important,’ when it may be several things acting in concert. It’s very difficult to study.”

The health problems marijuana can (and can’t) treat 
Cannabis and its many compounds are still being studied and probably will be for many years, so there is a lot that researchers still don’t know. Currently, though, evidence supports the use of cannabis or cannabinoids to treat the following conditions:

  • Certain types of pain
  • Seizure disorders
  • Stimulating the appetite in some patients
  • Spastic muscles in people with multiple sclerosis
  • Nausea and vomiting due to chemotherapy
  • Parkinson’s disease

Two cannabis-derived products called dronabinol and nabilone have FDA-approved indications to treat certain conditions, including chemotherapy-induced nausea and vomiting. And there is an FDA-approved prescription formulation of cannabidiol to treat certain types of seizures in children.

The science is less clear so far on whether it helps with the following:

  • Neurodegenerative diseases
  • Anxiety and post-traumatic stress disorder (PTSD)
  • Addiction
  • Cancer
  • Inflammation

With regard to cancer, there are some promising lines of research, but many of the studies are in mice. It’s still too soon to be sure of how best to use cannabinoids to help cancer patients. Just as cannabis contains many different compounds, “cancer” includes many different cancer types. So it will be important for researchers to sort out which compounds work, which don’t, and which might even cause harm, in specific types of cancer patients.

In at least one type of cancer, for instance, there is preliminary evidence that cannabinoids could accelerate the disease. Other studies suggest cannabis can interfere with chemotherapy and make people more vulnerable to viral infections. In fact, some scientists have pointed out that cannabis’ ability to suppress the immune system—and the potential dangers to immunocompromised people—is too often overlooked.

Another worrisome possibility is that people could develop cannabis use disorder (CUD), when people use it in a problematic way. Adolescents are much more prone than adults to developing CUD.  About 1 in 10 people who start smoking cannabis become addicted. A 2022 study published in JAMA Network Open found evidence that immediate use of medical cannabis by people with pain, insomnia, and symptoms of anxiety or depression increased the risk of CUD without helping them with most of their symptoms.

Responsible use 
If you use cannabis or cannabinoids, be aware of its other risks, which may include:

  • Interactions with other medications, especially those that affect your mood or make you drowsy
  • Interactions with alcohol, tobacco, or illicit drugs
  • Higher chance of bleeding if you’re on blood thinners
  • Effects on heart rate or blood pressure
  • Heart attack
  • Testicular cancer
  • Effects on your memory, judgment, and decision-making
  • Psychosis
  • Severe nausea and vomiting (cannabinoid hyperemesis syndrome, or CHS)
  • Lower birth weight if smoked during pregnancy
  • Lung injuries if THC is vaped
  • Fainting or falls upon standing up
  • Accidental poisonings, especially of children
  • Street cannabis laced with PCP or other drugs

Be aware, too, that due to spotty regulations and quality control, many seemingly innocent preparations of CBD oil are mislabeled or contaminated. In one 2020 study by the U.S. Food and Drug Administration, for example, scientists tested 147 CBD or hemp products being sold on the internet. Of 102 whose labels stated they had a certain amount of CBD, 18 had less than 80 percent of the advertised amount, while 37 had more than 120 percent of the advertised amount. The kicker: About half the samples also contained THC, which means that people using what they think are CBD products could inadvertently be intoxicated by THC.

The Department of Transportation has warned that using a CBD product will not be accepted as an explanation for a positive drug test. One truck driver reportedly lost his job this way.

Heavy metals have shown up in these products, leading in one case to a July 2020 nationwide recall due to lead contamination. Pesticides, microbes, and carcinogens have also been detected in some products.

Cannabis impairs driving, according to the National Institute on Drug Abuse, so if you’re using it it’s best not to get behind the wheel. It is also particularly detrimental to teenagers’ developing brains, impairing thinking and memory for days after use. 

Cannabis in some forms has a place in medicine—probably many places. But there is still a lot we don’t know, and fraudulent products are common. If you think medical cannabis might be right for you, protect yourself by consulting a qualified healthcare provider you trust.

Article sources open article sources

Bradford AC, Bradford WD. Medical Marijuana Laws Reduce Prescription Medication Use In Medicare Part D. Health Aff (Millwood). 2016;35(7):1230-1236.
Bradford AC, Bradford WD. Medical Marijuana Laws May Be Associated With A Decline In The Number Of Prescriptions For Medicaid Enrollees. Health Aff (Millwood). 2017;36(5):945-951.
Legare CA, Raup-Konsavage WM, Vrana KE. Therapeutic Potential of Cannabis, Cannabidiol, and Cannabinoid-Based Pharmaceuticals. Pharmacology. 2022;107(3-4):131-149.
Drug Enforcement Administration, Department of Justice. Schedules of Controlled Substances: Placement in Schedule V of Certain FDA-Approved Drugs Containing Cannabidiol; Corresponding Change to Permit Requirements. Final order. Fed Regist. 2018;83(189):48950-48953.
Drug Enforcement Administration, Department of Justice. Diversion Control Division. Controlled Substance Schedules. Accessed March 23, 2022.
Report to the U.S. House “Sampling Study of the Current Cannabidiol Marketplace to Determine the Extent That Products are Mislabeled or Adulterated Report in Response to Further Consolidated Appropriations Act, 2020,” FDA. July 2020.
United States Food & Drug Administration. Summitt Labs Issues Voluntary Nationwide Recall of KORE ORGANIC Watermelon CBD Oil Due to High Lead Results. July 28, 2020.
Evans DG. Medical Fraud, Mislabeling, Contamination: All Common in CBD Products. Mo Med. 2020;117(5):394-399.
Huestis MA, Solimini R, Pichini S, Pacifici R, Carlier J, Busardò FP. Cannabidiol Adverse Effects and Toxicity. Curr Neuropharmacol. 2019;17(10):974-989
United States Department of Transportation. DOT "CBD" Notice. February 18, 2020.
Montoya Z, Conroy M, Vanden Heuvel BD, Pauli CS, Park SH. Cannabis Contaminants Limit Pharmacological Use of Cannabidiol. Front Pharmacol. 2020;11:571832. Published 2020 Sep 11.
Martínez-Martínez E, Martín-Ruiz A, Martín P, Calvo V, Provencio M, García JM. CB2 cannabinoid receptor activation promotes colon cancer progression via AKT/GSK3β signaling pathway. Oncotarget. 2016;7(42):68781-68791.
Hazekamp A. The Trouble with CBD Oil. Med Cannabis Cannabinoids. 2018;1(1):65-72. Published 2018 Jun 12.
Seltzer ES, Watters AK, MacKenzie D Jr, Granat LM, Zhang D. Cannabidiol (CBD) as a Promising Anti-Cancer Drug. Cancers (Basel). 2020;12(11):3203. Published 2020 Oct 30.
O'Brien K. Cannabidiol (CBD) in Cancer Management. Cancers (Basel). 2022;14(4):885. Published 2022 Feb 10.
Epidiolex (cannabidiol). Greenwich Biosciences. Accessed March 23, 2022.
Badowski ME. A review of oral cannabinoids and medical marijuana for the treatment of chemotherapy-induced nausea and vomiting: a focus on pharmacokinetic variability and pharmacodynamics. Cancer Chemother Pharmacol. 2017;80(3):441-449.
Patel J, Marwaha R. Cannabis Use Disorder. [Updated 2022 Feb 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.
Gilman JM, Schuster RM, Potter KW, et al. Effect of Medical Marijuana Card Ownership on Pain, Insomnia, and Affective Disorder Symptoms in Adults: A Randomized Clinical Trial. JAMA Netw Open. 2022;5(3):e222106.
Khoury M, Cohen I, Bar-Sela G. "The Two Sides of the Same Coin"-Medical Cannabis, Cannabinoids and Immunity: Pros and Cons Explained. Pharmaceutics. 2022;14(2):389. Published 2022 Feb 10.
Kaiser Permanente. Medical Marijuana. November 8, 2021.
National Institute on Drug Abuse. Cannabis (Marijuana) Research Report. Does marijuana use affect driving? July 2020.
National Institute on Drug Abuse. Cannabis (Marijuana) Research Report. What are marijuana’s effects on other aspects of physical health?  July 2020.
National Institute on Drug Abuse. Cannabis (Marijuana) Research Report. Is there a link between marijuana use and psychiatric disorders? July 2020.
Silczuk A, Smułek D, Kołodziej M, Gujska J. The Construct of Medical and Non-Medical Marijuana-Critical Review. Int J Environ Res Public Health. 2022;19(5):2769. Published 2022 Feb 27.
Voelker R. FDA Says It Supports Cannabis Drug Development via Regulatory Pathways. JAMA. 2020;323(7):600.
Centers for Disease Control and Prevention. Marijuana and Public Health. Poisoning. Page last reviewed October 19, 2020.
National Center for Complementary and Integrative Health. Cannabis (Marijuana) and Cannabinoids: What You Need To Know. Last Updated November 2019.
Mayo Clinic. Medical marijuana. December 4, 2021.
United States Food & Drug Administration. FDA and Cannabis: Research and Drug Approval Process. October 1, 2020.
World Health Organization. Drugs (psychoactive): Cannabidiol (compound of cannabis).  December 19, 2017.
Federal Register. Schedules of Controlled Substances: Placement in Schedule V of Certain FDA-Approved Drugs Containing Cannabidiol; Corresponding Change to Permit Requirements. A Rule by the Drug Enforcement Administration on 09/28/2018.
American Cancer Society. Marijuana and Cancer. Last Revised August 4, 2020.

More On

Metformin: Could This Common Drug Prolong Your Life?

article

Metformin: Could This Common Drug Prolong Your Life?
Metformin, a common prescription drug that’s used to treat type 2 diabetes, is making headlines worldwide—but the big news has nothing to do with diab...
Surprising Reasons to Take Aspirin—and When to Skip It

slideshow

Surprising Reasons to Take Aspirin—and When to Skip It
From lowering cancer risk to boosting your beauty regimen, aspirin’s a versatile little pill. But it's important to know the potential side effects.
My Medication Looks Different. Should I Take It?

article

My Medication Looks Different. Should I Take It?
You pick up your prescription medication refill and head home. But when you take a dose from the new bottle, you notice that instead of the normal whi...
What Is CBD and Why Are so Many People Using It?

article

What Is CBD and Why Are so Many People Using It?
From vitamin store oils to online foot creams, cannabidiol (CBD) can be found just about everywhere these days, in a stunning array of products. Milli...
Track Your Meds and Save Money With Sharecare

article

Track Your Meds and Save Money With Sharecare
Do you have a prescription to treat a chronic condition? If so, you’re not alone. In fact, nearly 60 percent of Americans take at least one prescript...