Marijuana Myths


by Paul Hager
Chair, ICLU Drug Task Force

1. Marijuana causes brain damage

The most celebrated study that claims to show brain damage is the rhesus
monkey study of Dr. Robert Heath, done in the late 1970s. This study was
reviewed by a distinguished panel of scientists sponsored by the Institute
of Medicine and the National Academy of Sciences. Their results were
published under the title, Marijuana and Health in 1982. Heath’s work was
sharply criticized for its insufficient sample size (only four monkeys),
its failure to control experimental bias, and the misidentification of
normal monkey brain structure as “damaged”. Actual studies of human
populations of marijuana users have shown no evidence of brain damage. For
example, two studies from 1977, published in the Journal of the American
Medical Association (JAMA) showed no evidence of brain damage in heavy
users of marijuana. That same year, the American Medical Association (AMA)
officially came out in favor of decriminalizing marijuana. That’s not the
sort of thing you’d expect if the AMA thought marijuana damaged the brain.

2. Marijuana damages the reproductive system

This claim is based chiefly on the work of Dr. Gabriel Nahas, who
experimented with tissue (cells) isolated in petri dishes, and the work of
researchers who dosed animals with near-lethal amounts of cannabinoids
(i.e., the intoxicating part of marijuana). Nahas’ generalizations from his
petri dishes to human beings have been rejected by the scientific community
as being invalid. In the case of the animal experiments, the animals that
survived their ordeal returned to normal within 30 days of the end of the
experiment. Studies of actual human populations have failed to demonstrate
that marijuana adversely affects the reproductive system.

3. Marijuana is a “gateway” drug — it leads to hard drugs

This is one of the more persistent myths. A real world example of what
happens when marijuana is readily available can be found in Holland. The
Dutch partially legalized marijuana in the 1970s. Since then, hard drug use
— heroin and cocaine — have DECLINED substantially. If marijuana really
were a gateway drug, one would have expected use of hard drugs to have gone
up, not down. This apparent “negative gateway” effect has also been
observed in the United States. Studies done in the early 1970s showed a
negative correlation between use of marijuana and use of alcohol. A 1993
Rand Corporation study that compared drug use in states that had
decriminalized marijuana versus those that had not, found that where
marijuana was more available — the states that had decriminalized — hard
drug abuse as measured by emergency room episodes decreased. In short, what
science and actual experience tell us is that marijuana tends to substitute
for the much more dangerous hard drugs like alcohol, cocaine, and heroin.

4. Marijuana suppresses the immune system

Like the studies claiming to show damage to the reproductive system, this
myth is based on studies where animals were given extremely high — in many
cases, near-lethal — doses of cannabinoids. These results have never been
duplicated in human beings. Interestingly, two studies done in 1978 and one
done in 1988 showed that hashish and marijuana may have actually stimulated
the immune system in the people studied.

5. Marijuana is much more dangerous than tobacco

Smoked marijuana contains about the same amount of carcinogens as does an
equivalent amount of tobacco. It should be remembered, however, that a
heavy tobacco smoker consumes much more tobacco than a heavy marijuana
smoker consumes marijuana. This is because smoked tobacco, with a 90%
addiction rate, is the most addictive of all drugs while marijuana is less
addictive than caffeine. Two other factors are important. The first is that
paraphernalia laws directed against marijuana users make it difficult to
smoke safely. These laws make water pipes and bongs, which filter some of
the carcinogens out of the smoke, illegal and, hence, unavailable. The
second is that, if marijuana were legal, it would be more economical to
have cannabis drinks like bhang (a traditional drink in the Middle East) or
tea which are totally non-carcinogenic. This is in stark contrast with
“smokeless” tobacco products like snuff which can cause cancer of the mouth
and throat. When all of these facts are taken together, it can be clearly
seen that the reverse is true: marijuana is much SAFER than tobacco.

6. Legal marijuana would cause carnage on the highways

Although marijuana, when used to intoxication, does impair performance in a
manner similar to alcohol, actual studies of the effect of marijuana on the
automobile accident rate suggest that it poses LESS of a hazard than
alcohol. When a random sample of fatal accident victims was studied, it was
initially found that marijuana was associated with RELATIVELY as many
accidents as alcohol. In other words, the number of accident victims
intoxicated on marijuana relative to the number of marijuana users in
society gave a ratio similar to that for accident victims intoxicated on
alcohol relative to the total number of alcohol users. However, a closer
examination of the victims revealed that around 85% of the people
intoxicated on marijuana WERE ALSO INTOXICATED ON ALCOHOL. For people only
intoxicated on marijuana, the rate was much lower than for alcohol alone.
This finding has been supported by other research using completely
different methods. For example, an economic analysis of the effects of
decriminalization on marijuana usage found that states that had reduced
penalties for marijuana possession experienced a rise in marijuana use and
a decline in alcohol use with the result that fatal highway accidents
decreased. This would suggest that, far from causing “carnage”, legal
marijuana might actually save lives.

7. Marijuana “flattens” human brainwaves

This is an out-and-out lie perpetrated by the Partnership for a Drug-Free
America. A few years ago, they ran a TV ad that purported to show, first, a
normal human brainwave, and second, a flat brainwave from a 14-year-old “on
marijuana”. When researchers called up the TV networks to complain about
this commercial, the Partnership had to pull it from the air. It seems that
the Partnership faked the flat “marijuana brainwave”. In reality, marijuana
has the effect of slightly INCREASING alpha wave activity. Alpha waves are
associated with meditative and relaxed states which are, in turn, often
associated with human creativity.

8. Marijuana is more potent today than in the past

This myth is the result of bad data. The researchers who made the claim of
increased potency used as their baseline the THC content of marijuana
seized by police in the early 1970s. Poor storage of this marijuana in
un-air conditioned evidence rooms caused it to deteriorate and decline in
potency before any chemical assay was performed. Contemporaneous,
independent assays of unseized “street” marijuana from the early 1970s
showed a potency equivalent to that of modern “street” marijuana. Actually,
the most potent form of this drug that was generally available was sold
legally in the 1920s and 1930s by the pharmaceutical company Smith-Klein
under the name, “American Cannabis”.

9. Marijuana impairs short-term memory

This is true but misleading. Any impairment of short-term memory disappears
when one is no longer under the influence of marijuana. Often, the
short-term memory effect is paired with a reference to Dr. Heath’s poor
rhesus monkeys to imply that the condition is permanent.

10. Marijuana lingers in the body like DDT

This is also true but misleading. Cannabinoids are fat soluble as are
innumerable nutrients and, yes, some poisons like DDT. For example, the
essential nutrient, Vitamin A, is fat soluble but one never hears people
who favor marijuana prohibition making this comparison.

11. There are over a thousand chemicals in marijuana smoke

Again, true but misleading. The 31 August 1990 issue of the magazine
Science notes that of the over 800 volatile chemicals present in roasted
COFFEE, only 21 have actually been tested on animals and 16 of these cause
cancer in rodents. Yet, coffee remains legal and is generally considered
fairly safe.

12. No one has ever died of a marijuana overdose

This is true. It was put in to see if you are paying attention. Animal
tests have revealed that extremely high doses of cannabinoids are needed to
have lethal effect. This has led scientists to conclude that the ratio of
the amount of cannabinoids necessary to get a person intoxicated (i.e.,
stoned) relative to the amount necessary to kill them is 1 to 40,000. In
other words, to overdose, you would have to consume 40,000 times as much
marijuana as you needed to get stoned. In contrast, the ratio for alcohol
varies between 1 to 4 and 1 to 10. It is easy to see how upwards of 5000
people die from alcohol overdoses every year and no one EVER dies of
marijuana overdoses.


The Indiana Civil Liberties Union (ICLU) Drug Task Force is involved in
education and lobbying efforts directed toward reforming drug policy.
Specifically, we support ACLU Policy Statement number 210 which calls for
the legalization of marijuana. We also support an end to the drug war. In
its place, we favor “harm reduction” strategies which treat drug abuse as
what it is — a medical problem — rather than a criminal justice problem.

The Drug Task Force also works to end urine and hair testing of workers by
private industry. These kinds of tests violate worker privacy to no good
purpose because they detect past use of certain drugs (mostly marijuana)
while ignoring others (e.g., LSD) and cannot detect current impairment. In
situations where public and worker safety is a legitimate concern, we
advocate impairment testing devices which reliably detect degradation of
performance without infringing upon worker privacy.

For more information about the activities of the Drug Task Force, call the
ICLU at (317) 635-4059 or call Paul Hager at (812) 333-1384 or e-mail to
[email protected] on the InterNet.


  1. Marijuana and Health, Institute of Medicine, National Academy of
    Sciences, 1982. Note: the Committee on Substance Abuse and Habitual
    Behavior of the “Marijuana and Health” study had its part of the final
    report suppressed when it reviewed the evidence and recommended that
    possession of small amounts of marijuana should no longer be a crime (TIME
    magazine, July 19, 1982). The two JAMA studies are: Co, B.T., Goodwin,
    D.W., Gado, M., Mikhael, M., and Hill, S.Y.: “Absence of cerebral atrophy
    in chronic cannabis users”, JAMA, 237:1229-1230, 1977; and, Kuehnle, J.,
    Mendelson, J.H., Davis, K.R., and New, P.F.J.: “Computed tomographic
    examination of heavy marijuana smokers”, JAMA, 237:1231-1232, 1977.

  2. See Marijuana and Health, ibid., for information on this research. See
    also, Marijuana Reconsidered (1978) by Dr. Lester Grinspoon.

  3. The Dutch experience is written up in “The Economics of Legalizing
    Drugs”, by Richard J. Dennis, The Atlantic Monthly, Vol 266, No. 5, Nov
    1990, p. 130. See “A Comparison of Marijuana Users and Non-users” by Norman
    Zinberg and Andrew Weil (1971) for the negative correlation between use of
    marijuana and use of alcohol. The 1993 Rand Corporation study is “The
    Effect of Marijuana Decriminalization on Hospital Emergency Room Episodes:
    1975 – 1978” by Karyn E. Model.

  4. See a review of studies and their methodology in “Marijuana and
    Immunity”, Journal of Psychoactive Drugs, Vol 20(1), Jan-Mar 1988. Studies
    showing stimulation of the immune system: Kaklamani, et al., “Hashish
    smoking and T- lymphocytes”, 1978; Kalofoutis et al., “The significance of
    lymphocyte lipid changes after smoking hashish”, 1978. The 1988 study:
    Wallace, J.M., Tashkin, D.P., Oishi, J.S., Barbers, R.G., “Peripheral Blood
    Lymphocyte Subpopulations and Mitogen Responsiveness in Tobacco and
    Marijuana Smokers”, 1988, Journal of Psychoactive Drugs, ibid.

  5. The 90% figure comes from Health Consequences of Smoking: Nicotine
    Addiction, Surgeon General’s Report, 1988. In Health magazine in an article
    entitled, “Hooked, Not Hooked” by Deborah Franklin (pp. 39-52), compares
    the addictives of various drugs and ranks marijuana below coffeine. For
    current information on cannabis drinks see Working Men and Ganja: Marijuana
    Use in Rural Jamaica by M. C. Dreher, Institute for the Study of Human
    Issues, 1982, ISBN 0-89727-025-8. For information on cannabis and actual
    cancer risk, see Marijuana and Health, ibid.

  6. For a survey of studies relating to cannabis and highway accidents see
    “Marijuana, Driving and Accident Safety”, by Dale Gieringer, Journal of
    Psychoactive Drugs, ibid. The effect of decriminalization on highway
    accidents is analyzed in “Do Youths Substitute Alcohol and Marijuana? Some
    Econometric Evidence” by Frank J. Chaloupka and Adit Laixuthai, Nov. 1992,
    University of Illinois at Chicago.

  7. For information about the Partnership ad, see Jack Herer’s book, The
    Emperor Wears No Clothes, 1990, p. 74. See also “Hard Sell in the Drug
    War”, The Nation, March 9, 1992, by Cynthia Cotts, which reveals that the
    Partnership receives a large percentage of its advertizing budget from
    alcohol, tobacco, and pharmaceutical companies and is thus disposed toward
    exaggerating the risks of marijuana while downplaying the risks of legal
    drugs. For information on memory and the alpha brainwave enhancement
    effect, see “Marijuana, Memory, and Perception”, by R. L. Dornbush, M.D.,
    M. Fink, M.D., and A. M. Freedman, M.D., presented at the 124th annual
    meeting of the American Psychiatric Association, May 3-7, 1971.

  8. See “Cannabis 1988, Old Drug New Dangers, The Potency Question” by Tod H
    Mikuriya, M.D. and Michael Aldrich, Ph.D., Journal of Psychoactive Drugs,

  9. See Marijuana and Health, ibid. Also see “Marijuana, Memory, and
    Perception”, ibid.

  10. The fat solubility of cannabinoids and certain vitamins is well known.
    See Marijuana and Health, ibid. For some information on vitamin A, see “The
    A Team” in Scientific American, Vol 264, No. 2, February 1991, p. 16.

  11. See “Too Many Rodent Carcinogens: Mitogenesis Increases Mutagenesis”,
    Bruce N. Ames and Lois Swirsky Gold, Science, Vol 249, 31 August 1990, p.

  12. Cannabis and alcohol toxicity is compared in Marijuana Reconsidered,
    ibid., p. 227. Yearly alcohol overdoses was taken from “Drug Prohibition in
    the United States: Costs, Consequences, and Alternatives” by Ethan A.
    Nadelmann, Science, Vol 245, 1 September 1989, p. 943.

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