The use of cannabis as a medicine it is a practice that dates back to the times of ancient China. The first record of this practice appears in 2700 BC, where it was part of the Chinese pharmacopoeia, being indicated for the treatment of chronic pain, psychological disorders, rheumatic pain, diseases related to the female reproductive system, malaria, among others.1,2.

But the use of this plant for medicinal purposes is not limited to China, and records of this practice are found all over the world: in India its use started around 1000 BC (as an analgesic, anticonvulsant, anesthetic, anti-inflammatory , antibiotic, among other uses)2; there are records that the Assyrians also used this plant for medicinal purposes from the ninth century BC (for swelling and bruising, in the treatment for depression, attrition, among others)3; in Arabia, the use of cannabis as a diuretic, digestive, analgesic and antiepileptic has been reported since 1000 AD3,4; the use of cannabis for medicinal purposes has also occurred in Africa, at least since the 15th century, being used to treat malaria, fever, asthma, dysentery, among others5; the medical use of cannabis in the American continent started around the 16th century, where records indicate its use for the treatment of toothache and menstrual cramps.

The inclusion of cannabis in Western medicine is thought to have been due to the work of Irish physician William B. O'Shaughnessy and French psychiatrist Jacques-Joseph Moreau. O'Shaughnessy's influence stems from the publication of the article “On the preparations of the Indian hemp, or gunjah”, In 1839. This article was the result of his study of the plant, and it describes various cannabis-based preparations, assesses its toxicity in animals and assesses its use in patients with different pathologies, managing to demonstrate the therapeutic potential of cannabis . As for Moreau, his influence is due to the publication of the book “Du Hashish et in l'Alienation Mentale: Etudes Psichologiques”, Which results from the experiments he carried out with different cannabis-based preparations in an attempt to realize its potential in the treatment of mental illnesses. After its introduction into the western pharmacopoeia, cannabis started to be used for its analgesic, sedative, anticonvulsant, appetite stimulating, antibiotic and low toxicity properties. Reports of its efficiency in the treatment of various diseases and symptoms led to a wide use of this plant and its derivatives for therapeutic purposes. In the second half of the 19th century and the beginning of the 20th century, the scientific community corroborated in some way the initial reports of the therapeutic potential of cannabis. However, restrictive legislation that was adopted around the world since the 1930s ended the medicinal use of this plant (which was removed from the American pharmacopoeia in 1941)6,7.

The interest of the scientific community in cannabis reappeared when, in 1964, the structure to THC was identified by scientists Gaoni and Mechoulam8, originating a proliferation of studies about the active components of this plant that allowed a great learning about its pharmacology, biochemistry and clinical effects9. However, the reason for these effects was still unknown, the effects of cannabis on the brain and at the molecular level were not known. This changed when Allyn Howlett and William Devane identified the first cannabinoid (CB1) receptors present in the human body in 1988, causing community interest to soar during the 1990s. In fact, it was during this decade that another receptor was discovered of cannabinoids (called CB2) in 1992. R. Mechoulam, in collaboration with W. Devane, discovered a new neurotransmitter very similar to THC, an “endocannabinoid” that occurs naturally in the human body and attaches itself to cannabinoid receptors such as THC, called anandamine. Still in the 1990s, in 1995, the Mechoulam group discovered the second endocannabinoid, 2-arachidonnoylglycerol, or 2-AG. It was also in this decade that scientists, when tracing the metabolic pathways to THC, ended up discovering a hitherto unknown molecular signaling system that, however, regulates several biological functions - the endocannabinoid system (so named because of the plant that allowed its detection).

Since then, interest in medicinal cannabis has been steadily increasing. This conclusion is made possible by the continuous increase in scientific articles on this topic (which involves the study of cannabinoids, the study of its interaction with the endocannabinoid system, the study of the benefits attributed to cannabis, etc.), due to the interest of several pharmaceutical companies that have been betting on the development of therapies and drugs based on cannabis, but also by the fact that the legislation surrounding medical cannabis has been changing. Nowadays, several countries have already legislated the use of medical cannabis as therapy, Portugal being one of them.
In fact, the perception of the value and potential of the cannabis plant as a therapy has been changing. Currently, interest in this topic comes from all sides, from patients, to the medical community, to large pharmaceutical companies and to governments, which regulate its use. The scientific evidence that continues to accumulate has demonstrated the safety and efficiency of the use of cannabis and its derivatives as a treatment for various pathologies.
In Portugal, since January 2019, the use of drugs, preparations and substances based on the cannabis plant for medicinal purposes is regulated, through Decree-Law nº 8/2019.

  1. Brand EJ, et al. Cannabis in Chinese Medicine: Are Some Traditional Indications Referenced in Ancient Literature Related to Cannabinoids? Front Pharmacol. 2017 Mar 10; 8: 108.
  2. Touwn M. The religious and medicinal uses of cannabis in China, India and Tibet. J Psychoactive Drugs. 1981; 13 (1): 23-34.
  3. Aldrich M. History of therapeutic cannabis. In: Mathre ML, eds. Cannabis in medical practice. Jefferson, NC: Mc Farland; 1997. p. 35-55.
  4. Fankhauser M. History of cannabis in Western Medicine. In: Grotenhermen F, Russo E, eds. Cannabis and Cannabinoids. New York: The Haworth Integrative Healing Press; 2002. Chapter 4. p. 37-51.
  5. Du Toit BM. Cannabis in Africa. Rotterdam: Balkema; 1980.
  6. Mikuriya TH. Marijuana in Medicine. Presented as part of a Panel Discussion on Current Problems of Drug Abuse before the Second General Meeting at the 97th Annual Meeting of the California Medical Association, San Francisco, 23-27 March 1968.
  7. Zuardi AW. History of cannabis as medicine: a review. Rev Bras Psiquiatr. 2006; 28 (2): 53-7.
  8. Gaoni Y, et al Isolation structure and partial synthesis of an active constituent of hashish. J Am Chem Soc. 1964; 86_1646-7.
  9. Mechoulam RJ. Marijuana: chemistry pharmacology and clinical effects. New York: Academic Press. P. 2-99.
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