Medical Attributes of Cannabis sativa - Marijuana

by John Brady, Rachel Curtis, and Jared Nothstein
Wilkes University
Wilkes-Barre, PA

May, 2009
Commonly known as marijuana, hemp, pot, hashish, grass, or Mary Jane (USDA 2009), Cannabis sativa is a sprawling herb that is a member of the hemp family, Cannabaceae.  Thought to have evolved in China (Mikuriya 1969), it was introduced to the United States as early as 1629 (Boyce 1900, cited in Haney and Kutcheid 1975).  It can now be found growing throughout North America.  As of 2009, five states listed the plant as a noxious weed (USDA 2009).

Marijuana has been used as a medicinal plant throughout recorded history.  Chinese and Indian cultures used it since at least 1000 BCE (Mikuriya 1969), while Nicholas Culpeper included it in The English Physician (Hosking and Zajicek 2008).  It was used to treat complaints such as whooping cough, asthma, pain, and as a sedative (Fankhauser 2002 cited in Zuardi et al 2006). 

In the US, the plant may have originally been cultivated for use as a fiber and oilseed crop (Ranalli 1999).  However, it was also known for its ability to produce psychoactive effects.  In the 1930s, it was used throughout the Southern United States (Mikuriya 1969) and its notorious reputation as a psychoactive was broadened in the 1960s, when widespread use by young adults led to greater public and scientific interest in the drug (Jones 1977).  Since, 1970, marijuana has been considered a Schedule I substance under the Controlled Substances Act, defined as a drug “with no recognized medical use and great potential harm to the user” (Courtwright 2004, Lundberg 2005).  A great deal of research has been conducted pertaining to the medicinal benefits of Cannabis, particularly since the discovery of the active compounds and their respective receptors (Kalant 2008). 

Cannabis sativa contains cannabinoid compounds, a group of terpenophenolic compounds that are secondary metabolites (Capasso et al. 2008).  Cannabinoids are structurally related, and include cannabinol, cannabidiol, and Δ9-tetrahydrocannabinol (THC), all of which bind cannabinoid receptors throughout the body (Capasso et al. 2008).  Cannabinoid receptors are divided into CB1 and CB2: CB1 receptors are mainly found in the brain, but they can also be found in the kidneys, lungs, and liver (Brown 2007).  CB2 receptors are found in the immune system and hematopoietic cells (Brown 2007).  CB1 and CB2 are G-protein receptors, and when activated by cannabinoids, affect many intracellular structures such as calcium channels and protein kinase A (Takahashi et al. 2006) (Brown 2007).

Benefits of cannabinoids include the suppression of inflammation and various types of cell-mediated immunity (Weiss et al. 2006).  A study by Capasso et al (2008) found that cannabidiol selectively reduced hypermotility and spasms caused by induced inflammation in the small intestines of mice, making it a possible promising treatment for the symptoms of inflammatory bowel disease.

Due to recent research suggesting a link between THC and Alzheimer’s, Cannabis sativa may be a new mode of treatment for Alzheimer’s disease (Pacher et al 2006).  The mode of action for THC consists of competitive inhibition of the enzyme acetylcholinesterase (AChE).  Moreover, THC inhibits AChE-induced amyloid β-peptide (Aβ) aggregation, the prime pathological marker of Alzheimer’s disease (Eubanks et al 2006).  Ultimately, marijuana may be able to slow the progression of the disease and may serve as another mode of treatment for Alzheimer’s disease.

The cannabinoid compounds are an effective treatment for glaucoma (Tomida, et al 2004).  Cannabinoids lower intraocular pressure (IOP) by acting as vasodilators on blood vessels of the anterior uvea, thus relieving the symptoms of glaucoma (Tomida, et al 2004).  However, THC produces side effects, which currently exclude it as the preferred treatment for glaucoma because other drugs are as effective without producing side effects.  Side effects of Cannabis include reduction in systemic blood pressure and psychotropic effects (Tomida et al 2004).

Cannabis may also play a role in relieving nausea and vomiting of cancer patients undergoing chemotherapy.  This was proven through use of dronabinol, which is a synthetic form of THC approved by the US Food and Drug Administration (Galve-Roperh et al 2000, cited in Frazzetto 2003). Dronabinol has also been administered to increase the appetite of AIDS patients, so as to treat their anorexia and weight loss (Galve-Roperh et al 2000, cited in Frazzetto 2003).  THC may also be involved in treatment of malignant brain tumors; when THC was injected into malignant brain tumors in rats, the tumors were eliminated (Galve-Roperh et al 2000, cited in Frazzetto 2003).  Another area of therapeutic benefit may involve the ability of Cannabis to treat symptoms of multiple sclerosis, including muscle spasms and spasticity (Baker et al 2000, cited in Frazzetto 2003).

Side effects of cannabinoids include mood changes, respiratory and cardiovascular risks, and impairments of psychomotor performance (Ashton 2001).  Other side effects include anxiety and orthostatic hypotension (Kalant 2008).  The cannabinoids, however, vary in their psychoactivity: cannabinol is much less active than THC, and cannabidiol does not produce any psychoactivity (Hosking and Zajicek 2008).  Moreover, clinical trials have suggested the use of cannabidiol as a safe alternative treatment for schizophrenia. (Zuardi et al. 2006) The addictiveness of marijuana is also of concern: some report that withdrawal symptoms for marijuana resemble the symptoms of abstinence from alcohols and opiates.  They include nausea, vomiting, confusion, tachycardia, and sweating (Hasking and Zajicek 2008). 

While Cannabis has been found to confer many beneficial qualities, the fact that it is an illegal substance in the US, and has a variety of side effects must also be taken into serious consideration.  Since 1996, laws in eight states allowed the medical use of marijuana.  However, in 2001, the Supreme Court ruled that marijuana is an illegal drug despite state laws (Horn et al 2001).  As of 2009, the law prohibits the use of marijuana, even in medical cases.  Even if research does suggests a benefit to health from using marijuana, the legalization of the plant is hotly debated (Annas 1997, Watson et al. 2000, Robson 2001, Taylor 2003).  However, with advances in techniques of separation of beneficial compounds from hallucinogenic compounds, and the ability to test each compound found in the plant, it may be possible in the future to selectively extract certain compounds from the plant for use as medicinals.

LITERATURE CITED

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Baker, D., G. Pryce, J.L. Croxford, P. Brown, R.G. Pertwee, J.W. Huffman, & L. Layward.  2000. Cannabinoids control spasticity and tremor in a multiple sclerosis model.  Nature. 404:84-87.

Brown, A.  2007.  Novel cannabinoid receptors. British Journal of Pharmacology.  152:5; 567-575.

Capasso, R, F. Borrelli, G. Aviello, B. Romano, C. Scalisi, F. Capasso, & A.A. Izzo.  2008. Cannabidol, extracted from Cannabis sativa, selectively inhibits inflammatory hypermotility in mice.  British Journal of Pharmacology.  154:1001-1008.

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This paper was developed as part of the BIO 368 - Medical Botany course offered at Wilkes University during the spring of 2009. Course instructor was Kenneth M. Klemow, Ph.D. (kenneth.klemow@wilkes.edu). The information contained herein is based on published sources, and is made available for academic purposes only. No warrantees, expressed or implied, are made about the medical usefulness or dangers associated with the plant species in question.

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This page posted and maintained by Kenneth M. Klemow, Ph.D., Biology Department, Wilkes University, Wilkes-Barre, PA 18766. (570) 408-4758, kenneth.klemow@wilkes.edu.