There are marked differences in the knowledge on the medical uses of cannabis and cannabinoids in different diseases. For nausea and vomiting associated with cancer chemotherapy, anorexia and cachexia in HIV/AIDS, spasticity in multiple sclerosis and spinal cord injury there is strong evidence for medical benefits. For many other indications, such as epilepsy, movement disorders and depression there is much less available data.
Clinical studies with single cannabinoids or, less often with whole plant preparations (smoked marijuana, encapsulated cannabis extract) have often been inspired by positive anecdotal experiences of patients employing crude cannabis products. The anti-emetic, the appetite enhancing, relaxing effects, analgesia, and therapeutic use in Tourette's syndrome were all discovered in this manner.
Incidental observations have also revealed therapeutically useful effects in a study with patients with Alzheimer's disease wherein the primary issue was an examination of the appetite- stimulating effects of THC. Not only appetite and body weight increased, but disturbed behaviour among the patients also decreased. The discovery of decreased intraocular pressure with THC administration in the beginning of the 1970s was also serendipitous. For this reason, more surveys have been conducted in the past decade questioning individuals that use cannabis therapeutically.
(Institute of Medicine (U.S.A.)):
There is clearly a need for improved migraine medications. Sumatriptan is currently the best available medication for migraine headaches, but fails to completely abolish migraine symptoms in about 30 percent of migraine patents. Marijuana has been proposed numerous times as a treatment for migraine headaches (reviewed by Russo), but there are almost no clinical data on the use of marijuana or cannabinoids for migraine. Our search of the literature since 1975 yielded only one scientific publication on the subject. This report presents three cases in which cessation of daily marijuana smoking was followed by migraine attacks, which is not convincing evidence that marijuana relieves migraine headaches. (...) Various individuals have claimed that marijuana relieves their migraines, but at this stage there are no conclusive clinical data or published surveys about the effect of cannabinoids on migraines.
Joy JE, Watson SJ, Benson JA, eds. Marijuana and medicine: Assessing the science base. Institute of Medicine. Washington DC: National Academy Press, 1999.
I am a scientist at a medical school, studying basic cancer research. I suffer from severe migraine attacks. (...) About half of my migraine attacks are severe enough that I must spend the night in the hospital getting rehydrated by intravenous infusions, and given very powerful narcotics such as morphine or Demerol. Under my doctor's care, I tried every legally available migraine and anti-nausea drug (...). None had any effect at all on my symptoms. (...) After reading about chemotherapy patients using marijuana to treat similar sounding nausea, I tried smoking it as a treatment during an attack of migraine. Amazingly, it alleviated my symptoms, particularly the nausea, but the headache pain as well.
Website of Lester Grinspoon: http://www.rxmarihuana.com/migraines_hms.htm.
See also: Grinspoon L, Bakalar JB. Marihuana, the forbidden medicine. New Haven: Yale University Press, 1993, 1997. (Translated into several languages).
Cannabis has a documented history as a treatment for migraine dating back at least 1200 years to the work of Sabur ibn Sahl in Persia. Folk use in Sumeria and India may extend that figure back as much as 4000 years. Cannabis was a mainstream medicine in Europe and the USA for migraine between 1842 and 1942 before its prohibition under false pretenses. Cannabis has been shown to affect multiple migraine mechanisms via effects as an anti-inflammatory, and through several neurotransmitter systems (serotonin, dopamine, and glutamate), as well as by interactions with the endogenous opioid system. Many migraineurs report improvement with cannabis. This figure is about 80% in my experience.
More on cannabis in migraine in:
Russo EB. Cannabis for migraine treatment: The once and future prescription? An historical and scientific review. Pain 1998;76(1):3-8.
Russo EB. Hemp for headache: An in-depth historical and scientific review of cannabis in migraine treatment. J Cannabis Ther 2001;1(2):21-92.
Russo EB. Cannabis and Cannabinoids in Migraine Treatment. In: Grotenhermen F, Russo E, eds. Cannabis and Cannabinoids. Pharmacology, toxicology, and therapeutic potential. Haworth Press, Binghamton/New York 2001, in press.
(Wayne Hall, Nadia Solowij & Jim Lemon):
High doses of THC probably disturb the male and female reproductive systems in animals. They reduce secretion of testosterone, and hence reducing sperm production, motility, and viability in males. It is uncertain whether these effects also occur in humans. Studies in humans have produced both positive and negative evidence of an effect of cannabinoids on testosterone, for reasons that are not well understood. Hollister has argued that the reductions in testosterone and sperm production observed in the positive studies are probably of "little consequence in adults", although he conceded that they could be of "major importance in the prepubertal male who may use cannabis." The possible effects of cannabis use on testosterone and spermatogenesis may be most relevant to males whose fertility is already impaired for other reasons, e.g. a low sperm count.
(Please note: This text has been taken from a scientific article. Some sentences have been changed to improve understandability.)
Hall W, Solowij N, Lemon J. The Health and Psychological Consequences of Cannabis Use. National Drug Strategy Monograph Series No. 25. Canberra: Australian Government Publishing Service, 1994.
In human males, cannabis smoking has been shown to decrease blood levels of the three hormones LH, FSH, and testosterone. Moreover, an increased incidence of low sperm count has been reported in men who were heavy marijuana smokers. Other studies did not find measurable differences in men who were light or heavy marijuana users. Acute THC treatment produces a consistent and significant dose- and time-related decrease in LH and testosterone levels in male rodents. In the male rhesus monkey, an acute dose of THC produced a 65% reduction in blood testosterone levels by 60 min of treatment that lasted for approximately 24 hr.
(Please note: This text has been taken from a scientific text. Some sentences have been changed to improve understandability.)
Murphy L. Hormonal system and reproduction. In: Grotenhermen F, Russo E, eds. Grotenhermen, F., Russo, E. (eds.): Cannabis and cannabinoids. Pharmacology, toxicology, and therapeutic potential. Haworth Press, Binghamton/New York 2001, in press.
(Lynn Zimmer & John Morgan):
By giving large doses of THC to animals, researchers have produced appreciable effects on sex hormone levels. However, the effects vary from one study to another, depending on the dose and timing of administration. When effects occur, they are temporary. (...) In neither male nor female animals have researchers produced permanent harm to reproductive function from either acute or chronic marijuana administration. (...) There is no convincing evidence of infertility related to marijuana consumption in humans. There are no epidemiological studies showing that men who use marijuana have higher rates of infertility than men who do not. Nor is there evidence of diminished reproductive capacity among men in countries where marijuana use is common. It is possible that marijuana could cause infertility in men who already have low sperm counts, However, it is likely that regular marijuana users develop tolerance to marijuana's hormonal effects. (...) Marijuana has neither a masculinizing effect in females nor a feminizing effects in males.
Zimmer L, Morgan JP. Marijuana Myths Marijuana Facts. A review of the scientific evidence. New York/San Francisco: The Lindesmith Center, 1997.
(House of Lords):
Animal experiments have shown that cannabinoids cause alterations in both male and female sexual hormones; but there is no evidence that cannabis adversely affects human fertility, or that it causes chromosomal or genetic damage.
House of Lords Select Committee on Science and Technology. Cannabis. The scientific and medical evidence. London: The Stationery Office, 1998.