Medical Cannabis

Properties, benefits and side effects

Medical Cannabis

Is medical cannabis legal?

The legality of medical cannabis differs from country to country. Please refer to your local regulations for more information.

What is medical cannabis?

Medical cannabis is a category of medicinal products that uses the cannabis plant and/or its compounds as an add-on treatment for a variety of diseases, symptoms and medical conditions. The cannabis plant contains various chemicals, including more than 120 cannabinoids, called phytocannabinoids.

There are three main species of cannabis plant used for medical cannabis: Cannabis sativa is a taller plant mostly used in the West and grown in warmer regions; Cannabis indica is a shorter plant that is grown in cooler climates; and Cannabis ruderali is a small, quick-growing plant. However, the subdivision of cannabis into botanic varieties is scientifically disputed, given the continued crossing and hybridization. The debate about cannabis sorts is therefore called an unnecessary diversion in the literature: “Only biochemical and pharmacological differences are relevant”.1

This means that the best way to categorise cannabis for medical application is by its chemical varieties, or ‘chemovars’. Chemovars can be considered the chemical-pharmacological fingerprints of cannabis medication. Although it is difficult to precisely define chemovars for a natural product, the current most workable breakdown for medical cannabis is THC-rich, CBD-rich and THC-CBD balanced chemovars. 1

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What is medical cannabis used for?

Regulation on medical cannabis varies from country to country. It is prescribed usually as an add-on to other medical treatments, for conditions like chronic pain, multiple sclerosis, anxiety disorders and epilepsy; it can also be used for palliative cancer care. 2

Medical cannabis products have been approved in a number of countries for the treatment of seizures associated with severe forms of epilepsy such as Lennox-Gastaut syndrome, Dravet syndrome and tuberous sclerosis2, and for moderate to severe spasticity associated with multiple sclerosis.2 These treatment options include cannabidiol (CBD)-only medication and THC combined with CBD.3

The use of CBD and THC for medicinal purposes very much varies from country to country.

The endocannabinoid system

The endocannabinoid system, that consists at its core of endocannabinoids and cannabinoid receptors, extends throughout the whole body: brain, nervous system, organs, connective tissue, glands and immune cells4. Whilst CB1 is mainly expressed in the central and peripheral nervous system, CB2 occurs above all in the skin, bones and immune system. Both receptors are also expressed in numerous inner organs (see Illustration 1).

• Lungs
• Vascular system
• Muscles
• Gastrointestinal tract
• Gonads

• Spleen
• Bones
• Skin
• CNS + PNS (upregulated with inflammation)

• Lungs
• Vascular system
• Muscles
• Gastrointestinal tract
• Gonads

Illus. 1: Distribution of CB1- and CB2-receptors in the body.
CB = cannabinoid receptors PNS = peripheral nervous system CNS = central nervous system (Modified according to the Medical Cannabis Clinic, Australia)
4 Alger BE, Getting High on the Endocannabinoid System. Cerebrum. 2013 Nov 1;2013:14.

What are the main cannabinoids?

Cannabinoids are a group of chemically similar compounds which attach to the receptors of the body’s own endocannabinoid system.

They are divided into three groups based on their origin:

  • Endocannabinoids

These are produced in the human body or that of an animal

  • Synthetic cannabinoids

These do not occur in nature

  • Phytocannabinoids

These are mainly produced in the Cannabis sativa plant.

Phytocannabinoids are the most important constituent of medical cannabis as they can act on endocannabinoid receptors in the human brain and body to relieve the symptoms of some illnesses. The two main, best investigated phytocannabinoids are THC and CBD, which occur in comparatively high concentrations in the flowering shoot tips of Cannabis sativa.

Is medical cannabis different from hemp and marijuana?

Hemp is a strain of Cannabis sativa L. legally defined as containing no more than 0.3% THC on a dry weight basis, after the passage of the 2014 Agriculture Improvement Act (Farm Bill). The 2018 Farm Bill expanded the definition of hemp to include extracts, derivatives, and cannabinoids with less than 0.3% of THC by dry weight. Historically, hemp was grown for the fibrous materials found in stalks and oils in seeds. The flowering portions of the hemp plant may be used to extract phytocannabinoids, like CBD.

Medical cannabis and marijuana are very different things. Marijuana is the term used for cannabis primarily in the USA, and the term could have origins in Mexico. Medical cannabis, on the other hand, is a new category of medicinal products that uses the flowers of the cannabis plant or its compounds for medical purposes only.

Medical cannabis can lead to secondary effects including dizziness, altered heart rate, decreased blood pressure and blood sugar, increased appetite, reddened eyes, head and stomach ache, tiredness, poorer coordination/bodily tension, dry mucous membranes, short-term memory reduction, difficulties concentrating and changes in perception of time and space. If any of these effects occur, they usually decrease significantly or disappear completely some weeks after the initiation of the medical cannabis treatment.

  • Pregnancy or breastfeeding

In pregnant women, cannabinoids are known to pass through the placenta to the foetus and affect development. They can also pass via breast milk to infants in breastfeeding women and affect infant development. Therefore, medical cannabis is not recommended for pregnant or breastfeeding women.5,6

  • Children 

Use of medical cannabis in younger patients should be carefully considered by a physician prior to prescription.

Is medical cannabis addictive?

Few studies have been undertaken about addiction and medical cannabis. However, to minimize the risk of addiction, recommendations include balancing the content of THC to CBD, only using regulated prescribed medical cannabis and lowering daily cannabis use.7

Does medical cannabis affect driving?

Medical cannabis can affect the ability to stay alert, drive or operate heavy machinery. It is therefore important to understand your medical cannabis product and how the dosage can affect your ability to drive safely. It is recommended that you consult your physician before driving and taking medical cannabis.

How to take medical cannabis

What dosage of medical cannabis should I take?

The dosage suitable for you should be determined by your physician. Ideally, the dose should manage the symptoms without experiencing side effects. To ascertain this, your physician could suggest you start with a low dose that they may then increase if they need to, considering your type of medical cannabis product and the symptoms or condition you are suffering from.

What are the different ways to take medical cannabis

Medical cannabis can be taken in two ways:

  • Oral ingestion – Medical cannabis can be taken orally in the form of oils, tablets or capsules. The maximum effect of oral ingestion is typically only reached after several hours, but in turn, the maximum effect lasts longer than when medical cannabis is taken through inhalation. The maximum effect and duration of action of orally-taken medical cannabis is strengthened when taken with a meal.
  • Inhalation – The most frequent method for administration via inhalation is vaporisation. It is a fast and effective method for the systemic absorption of the active ingredients. When medical cannabis is inhaled, its effects are felt more quickly than with oral ingestion of a comparable dose, with a stronger, but shorter maximum effect.


Other pharmaceutical forms are not approved for medical cannabis use.

Where to buy medical cannabis

Medical cannabis is a prescription-only product that must be prescribed by a specialist physician. As the legislation for medical cannabis is different in every country, please consult your specialist and refer to local regulations for detailed information.

Can I travel with medical cannabis?

Rules for medical cannabis differ across the world, with it being authorized for use in some but not all countries. Even for those countries that do authorize the use of medical cannabis, regulations can differ on the quantity, type or strength of medical cannabis that can be used. If you are visiting another country and do not have paperwork from a physician to confirm that you need to take cannabis for medical reasons, it may be illegal to travel with it. It is recommended that you contact the embassy of the country you are visiting to understand their regulations for medical cannabis and, if flying, you should also get in touch with the airline you are travelling with to understand their policy on travelling with medical cannabis.

Scientific publications on medical cannabis

Research on medical cannabis is relatively recent.

Studies that have been conducted or are in progress are related to the use of medical cannabis in palliative care, the interactions of medical cannabis with other drugs, medical cannabis on driving impairment, among others.


1 Lewis MA, Russo EB, Smith KM. Pharmacological foundations of cannabis chemovars. Planta Med. 2018;84(4):225-233. doi:10.1055/s-0043-122240

2 European Monitoring Centre for Drugs and Drug Addiction. Medical use of cannabis and cannabinoids: questions and answers for policymaking. Published 2018. Accessed August 25, 2022.

3 Corey-Bloom J, Wolfson T, Gamst A et al. Smoked cannabis for spasticity in multiple sclerosis: a randomized, placebo-controlled trial. Can Med Assoc J. 2012;184(10):1143-1150. doi:10.1503/cmaj.110837

4 Alger BE. Getting high on the endocannabinoid system. Cerebrum. 2013;2013:14. Published 1 November 2013. Accessed 9 November 2022.

5 Dong C, Chen J, Harrington A, Vinod KY, Hegde ML, Hegde VL. Cannabinoid exposure during pregnancy and its impact on immune function. Cell Mol Life Sci. 2019;76(4):729-743. doi:10.1007/s00018-018-2955-0

6 Navarrete F, García-Gutiérrez MS, Gasparyan A, Austrich-Olivares A, Femenía T and Manzanares J (2020). Cannabis use in pregnant and breastfeeding women: behavioral and neurobiological consequences. Front Psychiatry. 11:586447.doi: 10.3389/fpsyt.2020.586447

7 Schlag A, Hindocha C, Zafar R, Nutt D, Curran H. Cannabis based medicines and cannabis dependence: A critical review of issues and evidence. J Psychopharmacol. 2021;35(7):773-785. doi:10.1177/0269881120986393