In an article, Medical marijuana: The science behind the smoke and fears, in The San Diego Union-Tribune, Professor Igor Grant at University of California San Diego claims that marijuana has therapeutic effects.
Professor William M. Bennett has addressed the following response to Grant´s article to The San Diego Union-Tribune:
Over the years more than 18,000 scientific papers have been published on marijuana/cannabis and only a handful have reported it to be safe and effective for any medical condition. The three recent studies Dr. Grant refers to were all done by the Center for Medicinal Cannabis Research and have a biased premise to start with regarding availability of funding. The National Institute of Alternative and Complementary Medicine funds peer-reviewed worthy research and has resources available to fund projects which meet criteria for valid medical research. It appears that marijuana studies by CMCR, founded in 2000, do not make the grade. The CMCR website lists 10 studies completed since that time and the results of six have been published. Media coverage of these few unremarkable studies has far outweighed coverage of the several thousand studies during these same ten years which have illuminated the many serious side effects associated with the use of marijuana, including more than 30 studies published between 2003 to 2005 strongly linking cannabis use to schizophrenia and other psychiatric problems. (see list of studies below)
In the three studies mentioned by Dr. Grant, he says that they were placebo controlled. A placebo for marijuana? In the book “Snake Oil Science – The Truth About Complementary and Alternative Medicine” author R. Barker Bausell writes extensively about the difficulty of discerning the placebo effect when it comes to the use complementary and alternative medicines because of the “expectation of benefit.” The criteria employed to identify valid studies include 1) publication in a high-quality journal, 2) the use of at least fifty patients per therapeutic group, 3) retention of at least 75 percent of the participants throughout the course of the study, and 4) employment of a credible placebo control. None of the published CMCR studies meet all of these criteria.
Further, the Food & Drug Administration states that for a drug to be approved for human use 1) The drug’s chemistry must be known and reproducible, 2) There must be adequate safety studies, 3) there must be adequate and well-controlled studies proving efficacy, 4) Acceptance by qualified experts is required, and 5) the scientific evidence must be widely available. There is simply no way to measure the dose or purity of smoked marijuana. Unless, of course, some of its more than 465 compounds are found to have medical benefit and can be extracted or replicated synthetically. Two of these, already available by prescription, are dronabinol and nabilone.
Marijuana, like many plant and animal matter, contains compounds that, when isolated and purified, can have therapeutic effects. Today we find that even the deadly poison causing botulism has been isolated for therapeutic use. However, no one would suggest recommending the bacteria causing botulism for self-medication. And several drugs have been developed from snake venom but that doesn’t mean a bite from the snake is safe.
There are myriad examples but the one thing they don’t have in common is the psychoactive and addictive effects of marijuana. And it is marijuana’s psychoactive properties that are its real attraction.
William M. Bennett. MD, MACP
Professor of Medicine & Clinical Pharmacology, Oregon Health & Sciences University, retired Past President, American Society of Nephrology
Scientific Research on Schizophrenia and Cannabis:
Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases. Br J Psychiatry. 2005 Dec;187:510-5
Toward a world consensus on prevention of schizophrenia.
Dialogues Clin Neurosci. 2005;7(1):53-67.
Risk for schizophrenia–broadening the concepts, pushing back the boundaries.
Schizophr Res. 2005 Nov 1;79(1):5-13.
The environment and schizophrenia: the role of cannabis use.
Schizophr Bull. 2005 Jul;31(3):608-12. Epub 2005 Jun 23.
Predictors of schizophrenia–a review.
Br Med Bull. 2005 Jun 9;73:1-15. Print 2005.
Cannabis as a risk factor for psychosis: systematic review.
J Psychopharmacol. 2005 Mar;19(2):187-94.
Cannabis use prior to first onset psychosis predicts spared neurocognition at 10-year follow-up.
Schizophr Res. 2005 Jun 1;75(1):135-7.
[Acute and chronic cognitive disorders caused by cannabis use]
Rev Prat. 2005 Jan 15;55(1):23-6; discussion 27-9. French.
Delta-9-tetrahydrocannabinol effects in schizophrenia: implications for cognition, psychosis, and addiction.
Biol Psychiatry. 2005 Mar 15;57(6):594-608.
Cannabis use and psychotic disorders: an update.
Drug Alcohol Rev. 2004 Dec;23(4):433-43. Review.
Is cannabis an anti-antipsychotic? The experience in psychiatric intensive care.
Hum Psychopharmacol. 2005 Apr;20(3):207-10.
Cannabis and risk of psychosis.
Swiss Med Wkly. 2004 Nov 13;134(45-46):659-63. Review.
[Cannabis can double the risk of schizophrenia. Increasing but still controversial knowledge of the psychological effects of the drug]
Lakartidningen. 2004 Oct 7;101(41):3126-7. Swedish.
Is the party over? Cannabis and juvenile psychiatric disorder: the past 10 years.
J Am Acad Child Adolesc Psychiatry. 2004 Oct;43(10):1194-205. Review.
Adverse effects of cannabis on health: an update of the literature since 1996.
Prog Neuropsychopharmacol Biol Psychiatry. 2004 Aug;28(5):849-63. Review.
Cannabis use and risk of psychosis: an etiological link?
Epidemiol Psichiatr Soc. 2004 Apr-Jun;13(2):113-9. Review.
[Cannabis and schizophrenia. From euphoria to psychosis]
Rev Med Liege. 2004 Feb;59(2):98-103. French.
Heavy cannabis users seeking treatment- prevalence of psychiatric disorders.
Soc Psychiatry Psychiatr Epidemiol. 2004 Feb;39(2):97-105.
Cannabis use and the risk of later schizophrenia: a review.
Addiction. 2004 Apr;99(4):425-30. Review.
Cannabis use and psychosis.Drug Alcohol Rev. 1998 Dec;17(4):433-44.
Cannabis use and age at onset of schizophrenia.
Am J Psychiatry. 2004 Mar;161(3):501-6.
Causal association between cannabis and psychosis: examination of the evidence.
Br J Psychiatry. 2004 Feb;184:110-7. Review.
[Cannabis use as a probable causative factor in the later development of schizophrenia]
Ned Tijdschr Geneeskd. 2003 Nov 1;147(44):2178-83. Dutch.
[Use of cannabis in adolescence and risk of schizophrenia]
Rev Bras Psiquiatr. 2003 Sep;25(3):131-2. Portuguese.
Cannabis use in adolescence and risk for adult psychosis: longitudinal prospective study.
BMJ. 2002 Nov 23;325(7374):1212-3. No abstract available.
[Is there a temporal correlation between substance abuse and psychosis in adolescents?]
Z Kinder Jugendpsychiatr Psychother. 2002 May;30(2):97-103. German.
Cannabis and psychosis.
Curr Psychiatry Rep. 2002 Jun;4(3):191-6. Review.
Cannabis-induced psychosis: a cross-sectional comparison with acute schizophrenia.
Acta Psychiatr Scand. 2002 Mar;105(3):173-8.
Cannabis and schizophrenia: a longitudinal study of cases treated in Stockholm County
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