Multiple sclerosis (MS) is a chronic degenerative disease of the central nervous system that causes inflammation, muscular weakness and a loss of motor coordination. Over time, MS patients typically become permanently disabled and, in some cases, the disease can be fatal. According to the US National Multiple Sclerosis Society, about 200 people are diagnosed every week with the disease -- often striking those 20 to 40 years of age.
Clinical and anecdotal reports of cannabinoids' ability to reduce MS-related symptoms such as pain, spasticity, depression, fatigue, and incontinence are plentiful in the scientific literature.[1-12] Most recently, investigators at the University of California at San Diego reported in 2008 that inhaled cannabis significantly reduced objective measures of pain intensity and spasticity in patients with MS in a placebo-controlled, randomized clinical trial. Investigators concluded that "smoked cannabis was superior to placebo in reducing spasticity and pain in patients with multiple sclerosis and provided some benefit beyond currently prescribed treatment." Not surprisingly, patients with multiple sclerosis typically report engaging in cannabis therapy, with one survey indicating that nearly one in two MS patients use the drug therapeutically.
Other recent clinical and preclinical studies suggest that cannabinoids may also inhibit MS progression in addition to providing symptom management. Writing in the July 2003 issue of the journal Brain, investigators at the University College of London's Institute of Neurology reported that administration of the synthetic cannabinoid agonist WIN 55,212-2 provided "significant neuroprotection" in an animal model of multiple sclerosis. "The results of this study are important because they suggest that in addition to symptom management, ... cannabis may also slow the neurodegenerative processes that ultimately lead to chronic disability in multiple sclerosis and probably other disease," researchers concluded. Spanish researchers in 2012 reported similar findings, documenting that "the treatment of EAE mice with the cannabinoid agonist WIN55,512-2 reduced their neurological disability and the progression of the disease."
Investigators have also reported that the administration of oral THC can boost immune function in patients with MS. "These results suggest pro-inflammatory disease-modifying potential of cannabinoids [for] MS," they concluded.
Clinical data reported in 2006 from an extended open-label study of 167 multiple sclerosis patients found that use of whole plant cannabinoid extracts relieved symptoms of pain, spasticity and bladder incontinence for an extended period of treatment (mean duration of study participants was 434 days) without requiring subjects to increase their dose. Results from a separate two-year open label extension trial in 2007 also reported that the administration of cannabis extracts was associated with long-term reductions in neuropathic pain in select MS patients. On average, patients in the study required fewer daily doses of the drug and reported lower median pain scores the longer they took it. These results would be unlikely in patients suffering from a progressive disease like MS unless the cannabinoid therapy was halting its progression, investigators have suggested.
In recent years, health regulators in Canada, Denmark, Germany, Spain and the United Kingdom have approved the prescription use of plant cannabis extracts to treat symptoms of multiple sclerosis. Regulatory approval in the European Union and in the United States remains pending.
 Rog et al. 2005. Randomized, controlled trial of cannabis-based medicine in central pain in multiple sclerosis. Neurology 65: 812-819.
 Wade et al. 2004. Do cannabis-based medicinal extracts have general or specific effects on symptoms in multiple sclerosis? A double-blind, randomized, placebo-controlled study on 160 patients. Multiple Sclerosis 10: 434-441.
 Brady et al. 2004. An open-label pilot study of cannabis-based extracts for bladder dysfunction in advanced multiple sclerosis. Multiple Sclerosis 10: 425-433.
 Vaney et al. 2004. Efficacy, safety and tolerability of an orally administered cannabis extract in the treatment of spasticity in patients with multiple sclerosis: a randomized, double-blind, placebo-controlled, crossover study. Multiple Sclerosis 10: 417-424.
 Zajicek et al. 2003. Cannabinoids for treatment of spasticity and other symptoms related to multiple sclerosis: multicentre randomized placebo-controlled trial [PDF]. The Lancet 362: 1517-1526.
 Page et al. 2003. Cannabis use as described by people with multiple sclerosis [PDF]. Canadian Journal of Neurological Sciences 30: 201-205.
 Wade et al. 2003. A preliminary controlled study to determine whether whole-plant cannabis extracts can improve intractable neurogenic symptoms. Clinical Rehabilitation 17: 21-29.
 Consroe et al. 1997. The perceived effects of smoked cannabis on patients with multiple sclerosis. European Journal of Neurology 38: 44-48.
 Meinck et al. 1989. Effects of cannabinoids on spasticity and ataxia in multiple sclerosis. Journal of Neurology 236: 120-122.
 Ungerleider et al. 1987. Delta-9-THC in the treatment of spasticity associated with multiple sclerosis. Advances in Alcohol and Substance Abuse 7: 39-50.
 Denis Petro. 1980. Marijuana as a therapeutic agent for muscle spasm or spasticity. Psychosomatics 21: 81-85.
 Jody Corey-Bloom. 2010. Short-term effects of cannabis therapy on spasticity in multiple sclerosis. In: University of San Diego Health Sciences, Center for Medicinal Cannabis Research. Report to the Legislature and Governor of the State of California presenting findings pursuant to SB847 which created the CMCR and provided state funding. op. cit.
 Clark et al. 2004. Patterns of cannabis use among patients with multiple sclerosis. Neurology 62: 2098-2010.
 Reuters News Wire. August 19, 2002. "Marijuana helps MS patients alleviate pain, spasms."
 Pryce et al. 2003. Cannabinoids inhibit neurodegeneration in models of multiple sclerosis. Brain 126: 2191-2202.
 de Lago et al. 2012. Cannabinoids ameliorate disease progression in a model of multiple sclerosis in mice, acting preferentially through CB(1) receptor-mediated anti-inflammatory effects. Neuropharmacology [E-pub ahead of print]
Killestein et al. 2003. Immunomodulatory effects of orally administered cannabinoids in multiple sclerosis. Journal of Neuroimmunology 137: 140-143.
Wade et al. 2006. Long-term use of a cannabis-based medicine in the treatment of spasticity and other symptoms of multiple sclerosis. Multiple Sclerosis 12: 639-645.
 Rog et al. 2007. Oromucosal delta-9-tetrahydrocannabinol/cannabidiol for neuropathic pain associated with multiple sclerosis: an uncontrolled, open-label, 2-year extension trial. Clinical Therapeutics 29: 2068-2079.
 William McGuinness. "Marijuana mouth spray Sativex may hit shelves by 2013." CBS News, January 26, 2012.