'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'
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 years 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 mice.
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 they developed.
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 found none.
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 marijuana.
The title of the report is "NTP Technical Report on the Toxicology
and Carcinogenesis Studies of 1-Trans-Delta(9)- Tetrahydrocanna-
binol (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.
Comment
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 literature.)
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.
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
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e-mail :aidsnews@aidsnews.org
Copyright (c) 1997 - John S. James.
