CAS No. 1972-08-3
August 3, 1972
Medical Marijuana - Unpublished Federal Study Found THC-Treated Rats
Lived Longer, Had Less Cancer ('AIDS Treatment News' Obtains 126-Page
Study, 'NTP Technical Report On The Toxicology And Carcinogenesis Studies
Of 1-Trans-Delta-9-Tetrahydrocannabinol, CAS No. 1972-08-3, In F344/N Rats
And B6C3F(1) Mice, Gavage Studies')
(ATN) Medical Marijuana: Unpublished Federal Study
Found THC- Treated Rats Lived Longer, Had Less Cancer
AIDS TREATMENT NEWS Issue #263, January 17, 1997; Published
twice monthly Subscription and Editorial Office: P.O. Box 411256 San
Francisco, CA 94141 800/TREAT-1-2 toll-free U.S. and Canada
415/255-0588 regular office number fax: 415/255-4659 Internet:
John S. James
AIDS TREATMENT NEWS has obtained a 126-page draft report of a
major toxicology study of THC, the main psychoactive ingredient of
marijuana. The study was completed over two and a half DECADES ago, and
passed peer review for publication, but has been kept quiet until this
month, when someone leaked copies of the draft report. As far as we
know, the public has never been told about this research -- for example,
the drug- reform movement seems not to have known about its existence.
This work may have been hushed because its findings are not what the
drug-war industry would want.
The study gave huge doses of THC to rats and mice by stomach tube,
and looked for cancers and other evidence of toxicity. First there were
small toxicity studies, which used enough THC to kill some of the
animals; later, two-year studies were run in both rats and mice, using
doses which were still much higher than those of marijuana smokers. The
two-year studies tested THC in several hundred rats and several hundred
In rats, those given THC had a clear survival advantage over the untreated
controls; this effect was statistically significant in all dose groups, and in
both males and females. In mice (which were given much larger doses
than the rats relative to body weight) there was no survival difference
among the groups -- except that those given the highest dose (which was
close to the lethal dose for mice) had worse survival.
In both mice and rats, in both males and females, "the incidence of benign
and malignant neoplasms ... were decreased in a dose-dependent manner"
-- meaning that the more THC the animals were given, the fewer tumors
The treated animals weighed less than the controls (even though both ate
about the same amount of food); the researchers speculated that the lower
body weight may have partly accounted for the increased survival and
reduced tumors in the THC-treated animals.
The doses were large enough to cause seizures and convulsions in many
of the animals, especially when they were dosed or handled. These did
not start immediately, but after many weeks, depending on the dose. The
researchers looked for brain lesions in animals which had seizures, but
No evidence of carcinogenic activity in the rats, but there was "equivocal
evidence" of one kind of thyroid tumor in the mice -- with no evidence of
a dose-dependent response. Other tumors were less common in the
treated animals than in the controls -- except in one case, which the
toxicologists believed was due to the fact that the treated animals lived
longer, and therefore had more opportunity to develop tumors.
The report includes a professionally objective review of the biological
effects, possible toxicities, and possible medical uses of THC and
The title of the report is "NTP Technical Report on the Toxicology and
Carcinogenesis Studies of 1-Trans-Delta(9)- Tetrahydrocannabinol (CAS
No. 1972-08-3) in F344/N Rats and B6C3F(1) Mice (Gavage Studies)."
Over 35 researchers contributed to this study, and 12 others reviewed
their work; several institutions, including the National Toxicology Program
and SRI International, were involved. The document we received is report
NTP TR 446, NIH Publication No. 94-3362, of the U.S. Department of
Health and Human Services. ("NTP" stands for National Toxicology
Program, which is made up of four Federal agencies within Health and
Human Services.) Each page of the draft is stamped "not for distribution
or attribution." In addition to the 126-page document we have reviewed
here, there are 11 appendices, which we have not seen.
According to the draft, the report will be available from NTP Central Data
Management, 919/541-1371. AIDS TREATMENT NEWS requested a
copy of the final report when it is ready, and also requested a copy of the
draft. Now that the existence of the report has become publicly known,
we have heard that draft copies are being sent if requested -- despite the
notice on each page not to distribute them.
It would be wrong to interpret this study as showing a beneficial or
protective effect of marijuana. The animals were given very large doses,
resulting in substantially lower body weight, which may itself have caused
much of the survival and tumor improvements. Also, this study used
THC, not marijuana smoke -- which like any smoke contains many
chemicals, some of which are likely to be harmful.
But the study does provide strong evidence that there is no significant
cancer risk (if any at all) from the main psychoactive ingredient of
marijuana; any such risk would be from incidental substances in the
smoke. And if there is such a risk, the modern high-potency marijuana
would likely reduce it, by reducing the amount of smoke required to
obtain the desired effect.
Also, there is no known case of any human death from overdose of
marijuana or THC, or from any other acute toxicity of these substances --
a remarkable safety record, compared with alcohol, aspirin, or many other
common drugs. (The toxicology report does not say there have been no
deaths, but the authors listed none, after doing an exhaustive survey of the
The literature review on the effects of THC and marijuana shows how
medical research has been politically skewed (although the paper itself
does not state this point). There are almost no studies of possible medical
uses of marijuana, but many studies looking for possible harm. Any
positive findings, therefore, can be used to support the drug war -- while
negative findings (those which fail to show any effect) are usually ignored.
Although many doctors and patients have reported important medical
benefits, scientific studies of medicinal use have seldom been allowed to
happen, since positive findings could challenge the official public- relations
tactic of demonization. The drug war itself has controlled the medical
research agenda, since it controls legal access to marijuana. Like most
permanent wars, it strives for self preservation.
The newly available Federal toxicology study provides the best evidence
yet that the risks of THC are small. What other drug would increase life
expectancy of rats when given in huge overdoses daily for two years? The
recent Federal attacks on medical marijuana -- against doctors and
desperately ill patients -- are needlessly cruel, and bizarrely inappropriate
to scientific and medical understanding.
Copyright (c) 1997 - John S. James. Distributed by AEGIS, your online
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