Medical Marijuana: Facts about cannabis, THC, and CBD

Exploring medical cannabis means becoming a highly educated consumer. You need to learn as much as you can from a variety of sources. This guide is intended to help you make a more-informed decision.This guide can’t tell you whether medical cannabis will alleviate your health conditions or symptoms. But it will provide basic information to help you consider whether medical cannabis is right for you, ideally working openly with your physician and other health care providers.

Medical Marijuana: Facts about cannabis, THC, and CBD Cover

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Did you know, nearly 2 million people reported using marijuana exclusively for medical reasons.

That number is only bound to increase as more and more states legalize the use of cannabis for medical purposes. But the popularity of this “new” treatment has created a flood of misinformation and false promises. Unscrupulous companies and marijuana enthusiasts are making claims it can treat everything from anxiety and depression, to inflammation, weight gain and even dementia.

But what are the facts? What are the proven benefits, and what are the risks? What’s the right dose, and how do you determine the quality of what you are taking? Do the products you’re buying even contain the ingredients they promise?

Don’t take chances with your health. Get accurate answers straight from the experts at Harvard Medical School in Medical Marijuana an all-new online report you can download right now.

  • Arthritis Pain? Studies show that medical marijuana is effective in relieving pain caused by arthritis as well as cancer, nerve damage, migraine and musculoskeletal diseases.
  • Trouble Sleeping? There is evidence of effectiveness for disturbed sleep associated with sleep apnea, fibromyalgia, chronic pain, and MS.
  • Anxious? The clinical evidence is limited, but medical marijuana can have a positive effect on conditions such as social anxiety and PTSD. New studies are currently underway
  • Nausea and Vomiting?  Talk to your doctor about FDA-approved cannabinoid-based prescription drugs that help with side-effects from chemotherapy.

Whether you are just investigating the potential health benefits for yourself, or are already using medical marijuana you will find the information you need to make the best decisions for your health in Medical Marijuana: Facts about cannabis, THC, and CBD.

This easy-to-understand report breaks down the science and answers your questions.

Looking for real pain relief? Before you head for the dispensary, discover which health issues are clinically proven to respond to Cannabis—there are only 3. The list is on page 7. 

Wondering how you can get medical cannabis?  Find out what you need to do to purchase it legally.

Are medical marijuana and CBD addictive? Will they cause side effects?

What’s the difference between single-compound and full-spectrum cannabis products? We’ll explain the differences and which might be most helpful for treating your symptoms.

How should I take it? Today you can find medical cannabis in everything from pills to gummies to lotions, and even special transdermal patches that can deliver cannabinoids (including THC and CBD) directly into the bloodstream. Download your report right now and turn to page 10 to decide the best variety for you.

From start to finish, this easy-to-understand guide spells out everything you need to know about medical marijuana and CBD. You’ll have all the information you need, so you can speak with your doctor about whether medical cannabis is something you should try. 

Download your report right now and discover:

  • The difference between CBD and THC—and which one is right for you.
  • Which medical benefits are clinically proven and which ones are nothing more than hype?
  • How to legally obtain the highest quality medical marijuana
  • Tips to spot marketing tricks some advertisers are using to sell CBD.
  • The potential risks and possible drug interactions of medical cannabis.
  • And, so much more!

Plus, on page 19 you’ll find an important caution for adults 55+. You’ll learn why people in this age group are more prone to side effects and drug interactions, which is why it’s critical to “start low and go slow” if you decide to give medical cannabis products a try.   

Before you purchase medical cannabis or a CBD product that promises relief from chronic pain, anxiety, arthritis, insomnia and depression, get the science-based facts and expert advice from Harvard Medical School.

Medical cannabis opens a world of new possibilities for patients, but it can be confusing. It’s more important than ever to be an educated consumer and that’s why I urge you to download this report today. Get the facts you need to make good decisions about medical cannabis for yourself and your loved ones.

Download now and you could be one step closer to the relief you seek, armed with the knowledge you need to be safe.


Prepared by the editors of Harvard Health Publishing in conjunction with Staci Gruber, PhD, Associate Professor of Psychiatry, Harvard Medical School and Director, Cognitive and Clinical Neuroimaging Core, and Director, Marijuana Investigations for Neuroscientific Discovery Program, McLean Hospital. (2020)

About Harvard Medical School Guides

Harvard Medical School Guides delivers compact, practical information on important health concerns. These publications are smaller in scope than our Special Health Reports, but they are written in the same clear, easy-to-understand language, and they provide the authoritative health advice you expect from Harvard Health Publishing.

  • Back to the future
  • Cannabis 101
  • How cannabis affects the mind and body
  • Does medical cannabis work?
  • Medical cannabis options
  • 1When it starts, how long it lasts
  • The CBD craze: Buyer beware
  • Who can get medical cannabis?
  • How to obtain medical cannabis
  • Common safety concerns
  • Long-term health risks
  • Resources

How to obtain medical cannabis

If you want to get permission to legally use medical cannabis under a medical marijuana program, it’s important to fully understand the terms of your state’s medical marijuana law or program. Whether you can access medical cannabis depends on what state you live in. The following information applies specifically to cannabis products obtained under state medical marijuana programs—not to hemp-derived (mostly CBD) products for sale online and in the general marketplace.

Comprehensive programs provide patients with legal protections, practical access to a variety of cannabis preparations, a variety of ways to administer cannabis products, and ongoing, public access to the program.

An additional 15 states have restricted, noncomprehensive programs. Many of these provide access to only low-THC, high-CBD cannabis preparations— for example, to treat seizures.

The National Conference of State Legislatures website maintains a list of state programs with links to the text of the laws themselves. It’s a good place to start educating yourself about medical marijuana laws: research/health/state-medical-marijuana-laws.aspx. Your state, if it has a medical marijuana law, may also have online information about the program. Following are some of the fundamentals of state medical cannabis laws and programs.


Doctors cannot “prescribe” cannabinoid-based products unless they are in the form of one of the four FDA-approved pharmaceuticals. Instead, a health care provider “certifies” you to legally obtain and use medical cannabis. In some states, this may be called getting authorization or a recommendation.

The person providing certification is usually a physician (M.D. or D.O.), who confirms that you have a qualifying condition—a health problem with symptoms that could, hypothetically, be alleviated by cannabis. You’ll probably need it in writing, but some states allow oral consent.

Other health care professionals who can certify in certain states include physician assistants, nurse practitioners, registered nurses, naturopaths, dentists, podiatrists, and nurse midwives. Some states also require a registered pharmacist to be at dispensaries to advise people on the appropriate cannabis preparation and delivery method for their qualifying conditions. You don’t necessarily have to get certified by your usual doctor. In fact, most primary care providers in the United States don’t offer this service. But you can also find physicians who specialize in providing access to medical cannabis. You may see them referred to as “marijuana doctors” or “medical marijuana clinics.”


States require you to be on an official list, or registry, as a certified medical cannabis user. You may be required to obtain a physical card. Or you may need to be added to a database that medical cannabis providers can check. You will probably pay a fee for registration, typically good for one year.

Caregiver access

Medical cannabis laws allow you to designate a primary caregiver. This person is an adult who acts as an intermediary to buy, deliver, and/or administer medical cannabis to certified patients. A caregiver can also grow the cannabis, or help the patient to do it. It can be a family member or friend, but is often a home health care provider or other medical professional.

Where you buy it

Some states allow privately run, for-profit cannabis dispensaries— brick-and-mortar facilities where a certified patient or caretaker can enter and buy products. You generally need to prove that you are certified to enter.

In other states, only nonprofit dispensaries are permitted. Or the state may allow people to obtain medical cannabis from nonprofit “collectives” in which multiple patients band together to produce and provide cannabis to themselves.

Some states allow patients to cultivate a limited number of cannabis plants for medical use.

State laws vary on how much cannabis you can possess at any given time. They may specify either actual ounces of products, an amount to last a certain period (often one month), or a limited number of living plants in cultivation.

Hemp-based products

You do not need to obtain certification to buy and use legally available hemp-based products containing CBD. But always keep in mind that these products are not (yet) regulated for purity and potency. In contrast, most states require that medical cannabis products sold in dispensaries undergo testing.

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