Medical Marijuana, also known as cannabis, is obtained from one of the oldest cultivated plants, Cannabis sativa. It has been used medicinally for thousands of years. The major active chemical in marijuana is THC, which is known chemically as tetrahydrocannabinol. THC and related chemicals are sometimes referred to as “cannabinoids.”
There is limited information about how common marijuana use is among people with MS, especially in the United States. In the United Kingdom, estimates of marijuana use in people with MS range from 4-8 %. Among people with a variety of medical conditions in Germany, Austria, and Switzerland, MS was the second most common medical reason for using marijuana (depression was the most common).
For more than a century, there has been controversy about the use of marijuana to treat MS and other medical conditions. The divergent opinions about the medical use of marijuana are apparent in the following quotations:
“There is not a shred of scientific evidence that shows that smoked marijuana is useful or needed. This is not medicine. This is a cruel hoax.” Gen. Barry McCaffrey, US drug czar, 1996
“The key point is that a cannabis-based medicine has not been scientifically demonstrated to be safe, efficacious, and of suitable quality.” British Minister of Health, 1997
“Marijuana’s therapeutic uses are well documented in the modern scientific literature.” L. Zimmer and J.P. Morgan, 1997
“Multiple sclerosis represents a promising target for cannabis-based medicines.” Leslie Iversen, British pharmacologist, 2000
Arguments favoring or opposing the medical use of marijuana may be politically driven and may not be based on a balanced view of the scientific and clinical evidence. This review provides an unbiased, fact-based assessment of our current understanding of the relevance of marijuana to MS.
In spite of a clear scientific rationale for using marijuana to treat MS symptoms and multiple reports of marijuana’s beneficial effects in MS, there is a scarcity of published clinical research in this area. Furthermore, none of the published studies have been large, well-designed clinical trials, and, consequently, definitive conclusions cannot be made. In some of the limited studies that have been reported, suggestive positive results have been obtained. These studies have used smoked marijuana as well as the pill forms, dronabinol (Marinol) and nabilone (Cesamet).
Promising results have been obtained in studies of spasticity, a type of muscle stiffness that occurs in MS. The muscle relaxant effects of marijuana were actually noted in the mid-nineteenth century in a medical report published by an Irish physician, Dr. William O’Shaughnessy. More recently, multiple studies indicate that marijuana and other cannabinoids may be effective in decreasing MS-related spasticity. The studies of marijuana and spasticity have not compared the effectiveness of marijuana to that of prescription medications for spasticity. A recent objective review of marijuana by the National Academy of Sciences/Institute of Medicine (NAS/IOM) concluded that marijuana may improve MS-associated spasticity.
Another symptom that may be relieved by marijuana is pain. Although there are no clinical studies that have specifically evaluated the effects of cannabinoids for MS-related pain, there are theoretical reasons why cannabinoids could relieve nerve-related pain. Also, limited studies of pain in people with other conditions and in experimental animals indicate that cannabinoids may have pain-relieving properties.
Variable results have been obtained in studies of other MS symptoms. Limited studies suggest possible improvement in tremor and bladder problems. In a study of one person with MS with jerky eye movements known as “nystagmus,” marijuana produced beneficial effects on three occasions while nabilone (Cesamet) and cannabis oil pills were not effective. Other MS symptoms have not shown a clear benefit in human studies. Importantly, marijuana may actually worsen walking unsteadiness.
In addition to this limited clinical research, two other types of studies have contributed information in this area. First, studies have evaluated the effects of cannabinoids on an experimental form of MS in research animals. Cannabinoids significantly decrease both tremor and spasticity in these animals. Second, to assess possible beneficial effects and patterns of use of marijuana in people with MS, a large survey was conducted in the late 1990’s in the United Kingdom and in the United States. In this study, 112 responses were obtained from questionnaires that were sent to 255 people with MS who used marijuana. More than 90% of the respondents felt that marijuana improved spasticity, pain, tremor, and depression. Improvement was noted by 70-90% for anxiety, tingling, numbness, weight loss, and leg weakness. On average, people had smoked marijuana for nearly six years, and marijuana was used almost three times daily for five-six days each week. There are significant limitations of this survey; it involved self-reporting of information, more than half of the questionnaires were not returned, and it was given to people who were already using marijuana.
Although THC itself has low short- and long-term toxicity, this does not appear to be the case for smoked marijuana. Smoked marijuana poses a variety of significant health risks, one of the most concerning of which is cancer. Marijuana smoke, like tobacco smoke, contains cancer-causing chemicals known as carcinogens. These toxic chemicals are present in the “tar” of marijuana smoke. By some estimates, marijuana smoke contains 50% more carcinogens than does tobacco smoke. There are anecdotal reports of marijuana smokers who have developed cancer of the lung or head and neck region at relatively young ages. Limited studies suggest that marijuana use may also increase the risk of other forms of cancer.
Various methods have been proposed to decrease the risk of cancer with marijuana smoking. An inhaled aerosol spray form has been developed and is currently being studied. “Vaporizers” are available, but there is little information about the relative amounts of THC and tar produced by these devices. It has been proposed that it might be possible to decrease the cancer risk by developing low-tar strains of cannabis plants or using specially designed filters.
Until safer methods are actually developed and are readily available, one technique that may be helpful for regular users is to smoke marijuana that contains a high concentration of THC. By using this type of marijuana, adequate blood concentrations of THC may be obtained with fewer puffs and thus less exposure to the potentially harmful smoke.
There are other risks related to marijuana smoking. Marijuana use has been associated with impaired lung function and increased risk of heart attack. Neurologically, marijuana may increase the risk of seizures and may produce memory difficulties, confusion, incoordination, and walking unsteadiness. Importantly, marijuana may decrease reaction time and thereby impair driving ability for up to eight hours after use. Although marijuana is not often thought of as an addictive drug, it is becoming increasingly apparent that regular marijuana users may indeed become dependent on it. Significant psychiatric conditions, such as schizophrenia, may be worsened by marijuana. Marijuana may lead to poor outcomes during pregnancy; since THC is excreted in breast milk, marijuana use should also be avoided during breast-feeding.
There is little information about how marijuana interacts with other drugs, particularly those that are used frequently in MS. Marijuana may increase the sedating effects of medications or alcohol. Also, there is one case of mania, a state of excessive arousal and excitability, that occurred when marijuana was taken in combination with fluoxetine (Prozac).
In its objective evaluation of the medical and scientific literature, the 1999 report by the National Academy of Sciences/Institute of Medicine (NAS/IOM) strongly cautioned against the long-term use of smoked marijuana, advised that prescription medications are available for many of the conditions treated with marijuana, and proposed that non-smoking methods be developed for using marijuana. The report concluded:
“Marijuana is not a completely benign substance. It is a powerful drug with a variety of effects. However, except for the harms associated with smoking, the adverse effects of marijuana use are within the range of effects tolerated for other medications.”
If marijuana is used, this use should be discussed with a physician and the user should be aware that there are prescription medications for many MS symptoms and that marijuana use for any purpose is illegal in most states and many other countries.