Anxiety, depression, nausea, suspicion, lethargy, memory loss, schizophrenia, infertility; these are just some of the potential side-effects .
But it's not all bad. Cannabis, to the scientific community, is an amazing compound. The drug, otherwise known as marijuana, is made up of over 400 different chemicals. Its most active ingredient affecting the brain is delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) is the drug's only non-psychoactive component.
Hemp, the type of plant from which cannabis is derived, historically had many functions. The seeds of the plant can be used in baking and the plant stalk can be used to manufacture fabric for clothes. Hemp is also found in plastics, oil-based paints, skin moisturisers and bird food. When it is dried and broken down, the pulp can be used to make paper and even work as fuel, albeit an inefficient one!
The body produces its own cannabis-like molecules - endocannabinoids. These molecules bind to specific sites on our cells called receptors, causing a series of chemical reactions. When cannabis binds to these receptors in the body, chemical reactions cause the mental and physical side-effects we can see.
Cannabis has many beneficial medicinal effects, (The most widely recognised being pain relief)
Large-scale clinical trials with those suffering from multiple sclerosis have revealed that the pain relieving properties of cannabis are particularly effective for this group. A University of Plymouth study led by John Zajicek in 2003 involving 630 participants showed that 60% of patients reported the cannabis-based treatment helped their pain and muscle stiffness after 15 weeks, compared to 48% of placebo patients.
Cannabis components have also shown some surprising, lesser-known medicinal effects. They have been hailed as everything from the potential cure for cancer to an allergy-buster.
Cancer Cure?
Brain tumours, one of the most aggressive forms of cancer, are currently treated by surgery but often the whole tumour is not removed and grows back, eventually killing the cancer patient. To prevent tumours growing from the site of earlier cancer surgery, all tumour cells need to be killed off and starved of nutrients.
Researchers have found that the cannabis component THC can do just that. Importantly, they found that the drug specifically targeted cancer cells and hardly affected healthy cells outside the tumour.
Dr Manuel Guzman, who led the study, said: "Cannabinoids seem to be selective anti-tumoral compounds as they can kill tumor cells without significantly affecting the viability of their non-transformed counterparts."
The study, published in Cancer Research in 2004, involved analysing removed cancerous tissue from brain tumour patients.
How does THC kill cancer cells?
Tumorous cells thrive on essential nutrients delivered via the blood. New blood vessels are formed through the process of angiogenesis to deliver blood and nutrients to the cancer. The signalling protein VEGF, Vascular Endothelial Growth Factor, is produced by the body to allow this new vessel-sprouting process to occur. THC inhibits the expression of genes needed to produce VEGF, thereby starving the tumour of nutrients needed for growth.
Guzman said: "Blockade of the VEGF pathway constitutes one of the most promising anti-tumoral approaches currently available. These findings provide a novel pharmacological target for cannabinoid-based therapies."
THC also induces apoptosis - the process of programmed cell death - in cancerous cells.
Guzman concluded: "The fair safety profile of THC, together with its possible growth-inhibiting action on tumour cells, may set the basis for future trials aimed at evaluating the potential antitumoral activity of cannabinoids."
Ease Heart Disease?
Substances responsible for lowering blood pressure also trigger the release of endocannabinoids. In 2001 the researchers Langneux and Lomontagne suggested that excess endocannabinoids could enhance this blood pressure lowering effect. They injected a drug to inhibit a cannabinoid receptor and reported a loss of the blood pressure lowering effect. This suggests that cannabinoids could be used to treat high blood pressure and heart disease.
A further study by Joyeux and colleagues in 2002 showed that cannabinoids could lower the severity of heart attacks in rodents.
Professor Jeremy Pearson, Associate Medical Director at the British Heart Foundation (BHF) said: "There is increasing experimental evidence that cannabinoid drugs may be useful in limiting damage to diseased hearts or blood vessels, though much more work needs to be done to understand how effective these drugs may be compared to current cardiovascular drugs. We also need to look at what their side effects are likely to be before clinical trials could take place."
Allergies and other Uses?
In addition to possibly treating depression, obesity and nicotine addiction, cannabinoids can also be used in allergy creams. Although the way in which this works is not known, Andreas Zimmer and colleagues in 2007 found the expression of genes involved in the inflammatory allergic response were changed as a result of the application of a cannabis-based cream.
Cannabis - The Political Debate
Cannabinoids are a promising group of drugs that have been implicated in various fields of clinical research. However, legal issues surrounding the drug have scared off researchers from working in this field, particularly in the United States., Cannabinoid research joins stem cell research and xenotransplantation - the transplantation of an organ from one species to another - on the list of potentially life-saving technologies that have been held back for legal reasons.
The Multidisciplinary Association for Psychedelic Studies (MAPS) hold a different view from many of these researchers. They are an independent US-based research funding body and aim to "initiate and fund a serious drug development research program aimed at proving to the satisfaction of the FDA (the US Food and Drug Administration) that marijuana is safe and efficacious for specific medical uses and should become a legal, FDA-approved prescription medicine."
They claim that "The National Institute on Drug Abuse (NIDA) has a monopoly on the supply of marijuana that can be used in research, provides low-potency material, and only makes it available to projects it approves. MAPS needs its own independent source of supply since NIDA's arbitrary and lengthy review process for providing marijuana essential to research can derail any drug development plan."
Is this the way forward? Should more money be invested in cannabinoid research? Perhaps. But this should be done with caution. As in the case of MAPS, a political motive can sometimes override scientific interests. This exciting field in clinical research is definitely one to keep an eye on.
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