Marijuana Myths/Marijuana Facts
A Review Of The Scientific Evidence
By Lynn Zimmer, PH.D. & John P. Morgan, M.D.
The War On Drugs stands on the legs of prohibition.
Knock those pins down and the whole scarecrow tumbles.
Which is why the federal government, combined with
greedy and/or racist corporate interests, has worked so
hard to promote the myths that keep the American public
scared to death of cannibas.
In their new book, "Marijuana Myths, Marijuana Facts",
authors Lynn Zimmer and John P. Morgan scrutinize the
"scientific" literature on which those myths are based, in
the most comprehensive study of marijuana myths done to
date. Each of the books 20 chapters deals with one myth
and the literature behind it. In this excerpt, we've (HIGH
TIMES editors...e.j.) culled 17 of them, which vary slightly
from the final published version. For those who want to
examine the actual studies that were cited to promote the
myths, the book is available from the Lindesmith Center (I
chose not to publish the price or phone number that
appeared in HT)
Myth Number 1
Marijuana's harms have been proved scientifically. In the 1960's and 70's,
many people beleived that it was harmless. Today we know that marijuana is
mucc more dangerous than previously beleived.
In 1972, after reviewing the scientific evidence, the National Commission on
Marijuana and Drug Abuse (the Shafer Commission) concluded that while
marijuana was not entirely safe, its dangers had been grossly overstated.
Since then, scores of additional studies have been conducted. None has
revealed dramatically different findings from those reviewed by the Shafer
Commission in 1972. In 1995, based on 30 years of scientific research, the
editors of the British medical journal "Lancet" concluded that "the smoking
of cannibas, even long term, is not harmful to health."
Myth Number 2
Marijuana is more potent today than in the past. Adults who used marijuana
in the 1960's and 70's often fail to realize that when today's youth use it they
are using a much more dangerous drug.
When today's youth use marijuana, they are using the same drug used in the
1960's and 70's. A small number of low-THC (Delta-9
Tetrahydrocannabonal...e.j.) samples seized by police in the early 1970's are
often used to calculate a dramatic increase in potency. However, these
samples were not representative of the marijuana generally available to users
during that era. Potency data in the 1980's to the present are more reliable,
and they show no increase in the average THC content of marijuana. Even if
marijuana potency were to increase, it would not make the drug more
dangerous. THC itself does not cause damage to organs and tissues, and
adverse psychological reactions from marijuana appear to be largely
unrelated to potency.
Myth Number 3
Marijuana-related hospital emergencies are increasing, particularly among
youth. This is evidence that marijuana is causing more harm than previously.
When patients in an E.R. report using marijuana, the visit may be recorded
as marijuana-related, even if marijuana did not cause the immediate medical
condition. Teenagers in hospital E.R.s have always mentioned marijuana
more frequently than heroin or cocaine because heroin and cocaine are rarely
used by teenagers (like we can afford it...e.j.). In all age groups, marijuana
"mentions" have increased since 1992, but in the 80% of the cases when
marijuana is mentioned, other drugs are mentioned as well. In 1994, fewer
than 2% of drug-related E.R. visits involved the use of marijuana alone
(8,318 of a total of 518,521).
Myth Number 4
Marijuana is highly addictive. Long term users experience physical
dependence and withdrawal, and often need professional drug treatment to
break their marijuana habits.
Most marijuana users use the drug occasionally, never become dependant
and never experience symptoms of withdrawal. Heavy users often stop
without difficulty, and if they describe withdrawal symptoms at all, those
symptoms are remarkably mild. Some marijuana users identify themselves as
addicts, and they may seek help from drug treatment professionals. However,
an important reason for the recent dramatic increase in people entering
treatment programs for "marijuana problems" is that marijuana users who
are identified through drug-testing in the workplace must often participate in
outpatient drug treatment to avoid being fired.
Myth Number 5
Marijuana has no medicinal value. Safer, more effective drugs are available,
including a synthetic version of THC, marijuana's primary active ingredient,
which is marketed in the United States under the name Marinol.
There are legitimate medical uses of marijuana, and many patients currently
use it despite it's illegallity. It has been proven effective in reducing nausia
induced by cancer chemotherapy, stimulating appetite in AIDS patients and
reducing intraocular pressure in people with glaucoma. There is also
appreciable evidence that marijuana reduces muscle spasticity in patients
with neurological disorders. Other theraputic uses, currently supported by
anecdotal evidence, may eventually be proven. Although a synthetic THC
capsule is now available, for many patients it is not as effective as smoked
marijuana, and it often produces more unpleasant psychoreactive side
effects. The federal government's continuing opposition to legalizing
marijuana for medical purposes is based on political rather than scientific
Myth Number 6
Marijuana's active ingredient, THC, gets trapped in body fat. Because THC
is released from fat cell slowly, subtle psychoreactive effects may last for days
or weeks following use. THC's long persistance in the body damages organs
that are high in fat content, the brain in particular.
Many active drugs enter the body's fat cells. What is different (but not
unique) about THC is that it exits the fat cells slowly. As a result, traces of
marijuana can be found in the body for days or weeks after ingestion.
However, within a few hours of smoking marijuana, the amount of THC in
the brain falls below the concentration required for detectable psychoactivity.
The fat cells in which THC lingers are not harmed by the drug's presence; nor
is the brain or other bodily organs. The most important consiquence of
marijuana's slow excretion is that it can be detected in blood, urine and
tissue long after it is used.
Myth Number 7
Marijuana use impairs the immune system. Users are at increased risk of
infection, including from HIV. AIDS patients are particularly vulnerable to
marijuana's immune effects because their immune systems are already
There is no evidence that marijuana makes users more susceptible to viral,
bacterial, parasetic or fungal infections. Nor is there evidence that it lowers
users' resistance to sexually transmitted diseases (STD's). Early studies, which
showed decreased immune function in cells taken from marijuana users, have
since been disproved. Animals exposed to THC have increased rates of
infection, but only with extremely large doses, and such studies have little
relevance to humans. Even among people with existing immune disorders,
such as AIDS, marijuana appears to be relatively safe. However, the recent
association between tobacco-smoking and lung infection in AIDS patients
warrants further research into possible harm from the smoking of marijuana
in immune-supressed persons.
Myth Number 8
Marijuana is more damaging to lungs than tobacco. Marijuana smokers are
at high risk of developing lung cancer, bronchitis and emphysema.
Moderate smoking of marijuana appears to pose minimal danger to the
lungs. Like tobacco smoke, marijuana smoke contains a number of irritants
and carcinogens. But marijuana smokers typically inhale much less smoke:
therefore, the risk of serious lung disease is lower. Daily high dose marijuana
have some of the same adverse respiratory symptoms as tobacco smokers.
There have been no reports of lung cancer related solely to marijuana, but
because researchers have found precancerous changes in cells taken from the
lungs of heavy smokers, the risk of cancer is present. Unlike heavy tobacco
smokers, heavy marijuana smokers exhibit no obstruction of the lung's small
airways, a condition associated with emphysema.
Myth Number 9
Marijuana interferes with male and female sex hormones. In both men and
women it can cause infertility. In adolescents, marijuana reards sexual
development and may produce feminine characteristics in males and
masculine characteristics in females.
There is no evidence that marijuana causes men or women to be infertile. In
animal studies, high doses of THC diminish the production of some sex
hormones and can impair reproduction. However, most studies of humans
have found that marijuana has no impact on sex-hormone levels. And in
those studies showing an impact, it is modest, temporary and of no apparent
consequence for reproductive capacity. There is no scientific evidence that
marijuana interferes with adolescent sexual development. Claims that it has a
feminizing effect on males and a masculinizing effect on females-apparently
designed to frighten adolescents away from marijuana experimentation-are
close to pure fabrication.
Myth Number 10
Marijuana use during pregnancy damages the fetus. Prenatal marijuana
exposure causes birth defects in babies and, as they grow older,
developmental problems. The health and well-being of the next generation is
threatened by marijuana use by pregnant women.
Studies of newborns, infants or children show no consistent physical,
developmental or cognitive effects deficits related to parental marijuana
exposure. Marijuana has no reliable impact on birth size, length of gestation,
neurological development or the occurance of physical abnormalities. In
older children, the administration of hundreds of tests has revealed only
minor differences between the offspring of marijuana users and nonusers-and
some are positive rather than negative in nature. Given that there is no
evidence of functional impairment among marijuana-exposed children, the
occasional negative finding is, in all likelihood, a statistical artifact of the
Myth Number 11
Marijua kills brain cells. Used over time, marijuana permanently alters brain
structure and function, resulting in memory loss, cognitive impairment,
personality deterioration and reduced productivity.
None of the medical tests currently used to detect brain damage in humans
has found harm from marijuana, even with long-term high-dose use. An
early study reported brain damage in rhesus monkeys after six months
exposure to high concentrations of marijuana smoke. But in a recent, more
carefully conducted study, researchers found no evidence of brain
abnormality in monkeys that were forced to inhale the equivalent of four to
five marijuana cigarettes everyday for a year. The claim that marijuana kills
brain cells is based on a speculative report dating back a quarter of a century
that has never been supported by scientific study.