279 lines
14 KiB
Plaintext
279 lines
14 KiB
Plaintext
The Health Effects of Marijuana on Humans
|
|
|
|
|
|
Introduction
|
|
|
|
Marijuana has been used as a drug since the beginning of
|
|
time, yet there are still many mysteries about its health
|
|
effects on humans. Marijuana, or cannabis sativa, is a
|
|
preparation of the crushed flowers and buds of female hemp
|
|
plant. The existence of the plant has been reported as
|
|
early as 1500-1200 BC. in China, and cannabis has been
|
|
described as an analgesic as early as 200 AD (Walton, 1938).
|
|
Since then, an overwhelming number of studies have attempted
|
|
to explain the physical and psychological effects of
|
|
cannabis on humans.
|
|
|
|
Physical Effects
|
|
|
|
Physically, cannabis is relatively harmless. Studies
|
|
have observed interesting results, including that it causes
|
|
structural changes in the brain, depresses male sperm
|
|
counts, causes chromosome damage, lowers testosterone
|
|
levels, and damages the lungs. Most of these claims,
|
|
however, have been unreplicated in humans or have been
|
|
contradicted by other work. This section will address each
|
|
of these reported negative side-effects.
|
|
Various studies have claimed that cannabis destroys brain
|
|
cells (Landfield et al., 1988; Haper et al., 1977; Meyers
|
|
and Heath, 1979; Heath et al., 1980). However, several
|
|
other studies found no structural or neurochemical atrophy
|
|
in the brain at all (Cabral et al., 1991; Paule et al.,
|
|
1992; Co et al., 1977; Kuehnle, 1977). Furthermore, it
|
|
should be noted that Heath's work was sharply criticized for
|
|
avoiding safeguards of bias and reporting "changes" that
|
|
occur normally in the mammalian brain (Natl. Acad. of
|
|
Sciences, Inst. Medicine, 1982).
|
|
Wu et al. (1988) found a correlation between cannabis use
|
|
and low sperm counts in human males. This is misleading
|
|
because a decrease in sperm count has not been shown to have
|
|
a negative effect on fertility and because the sperm count
|
|
returns to normal after cannabis use has stopped. (Natl.
|
|
Acad. Sciences, Inst. Medicine, 1982)
|
|
Another claim made was that cannabis causes chromosome
|
|
breakage. The primary source for this are studies that were
|
|
conducted by Dr. Gabriel Nahas in the early 1980s. Nahas
|
|
observed abnormalities in somatic (not sex) cells of rhesus
|
|
monkeys in vitro (i.e., in test tubes and petri dishes) and
|
|
then made the unjustified conclusion that these changes
|
|
would occur in human bodies in vivo (in the body). Nahas'
|
|
work was criticized by his colleagues and, in 1983, he
|
|
backed away from his own conclusions.
|
|
A widely held claim has also been that cannabis lowers
|
|
male testosterone levels (Kolodny, 1974). This theory has
|
|
been challenged by several studies (Block, 1991; Mendelson
|
|
et al., 1974; Coggins et al., 1976) that found no
|
|
correlation at all. Marijuana and Health (Natl. Acad.
|
|
Sciences, Inst. Medicine, 1982), also, after reviewing
|
|
literature at that time, concluded that "Due to conflicting
|
|
and incomplete evidence, it is not possible to conclude at
|
|
the present time whether marijuana smoking has a significant
|
|
effect upon gonadotropic and testosterone concentrations in
|
|
humans."
|
|
The most serious physical danger of using cannabis is in
|
|
smoking it. Inhaling any sort of burnt plant matter is not
|
|
very good for the lungs. Tashkin et al. (1990) reports
|
|
decreased gas exchange capacity and the existence of
|
|
particle residue in the lungs of marijuana smokers several
|
|
times greater than for tobacco smokers. Wu et al. (1988)
|
|
noted that marijuana is several times more carcinogenic than
|
|
tobacco. These findings, though, must be interpreted with
|
|
caution. In both studies, smoked marijuana was not
|
|
filtered, while smoked tobacco was. Tashkin et al. notes
|
|
that, "these differences could largely account for more than
|
|
twofold greater tar yield from marijuana than tobacco that
|
|
was measured using syringe-simulated puffs of similar volume
|
|
and duration." Smoking cannabis through a water-pipe will
|
|
filter out water soluble carcinogens and will also greatly
|
|
cool down the smoke. Furthermore, cannabis need not be
|
|
smoked: In Middle Eastern countries, it has been consumed
|
|
through teas and food for centuries, avoiding the
|
|
carcinogenicity of smoke altogether.
|
|
Despite cannabis' known negative effects to lung
|
|
function, it has never been reported to cause a single
|
|
instance of lung cancer. Tobacco, though, is expected to
|
|
kill 400,000 people this year (Glenn, 1992). If cannabis is
|
|
so much more dangerous to a user's lungs than tobacco and is
|
|
so much more carcinogenic, why aren't there stacks of
|
|
reports of cannabis-induced lung cancer? One interesting
|
|
theory is that it's because tobacco tars are significantly
|
|
radioactive, while marijuana tars aren't at all. Winters et
|
|
al. (1982) found that a pack-and-a-half-a-day smoker of
|
|
tobacco is exposed to 8000 mrem of radiation a year, equal
|
|
to the dose of 300 chest x-rays. A more recent study
|
|
indicates that a pack-and-a-half-a-day smoker receives 16000
|
|
mrem of radiation more than a non-smoker, annually (NCRP
|
|
Report #95, 1987). It could also be noted that the mere
|
|
contents of carcinogenic chemicals doesn't necessarily
|
|
indicate an extreme health hazard. For example, roasted
|
|
coffee contains 800 volatile chemicals, of which only 21
|
|
have been tested on rodents, and of those, 16 were
|
|
carcinogenic (Ames, 1990). Coffee has never been considered
|
|
a great cancer-causing substance, though.
|
|
Cannabis has also been known for its many therapeutic
|
|
uses, including the treatment of open angle glaucoma,
|
|
asthma, and the nausea associated with chemotherapy. It has
|
|
also been described as a tumor retardant, an antibiotic, a
|
|
sleep-inducer, and a muscle relaxant (Cohen, 1980).
|
|
|
|
Psychological Effects
|
|
|
|
The psychological effects of cannabis use have been
|
|
described quite many years before the physical effects, yet
|
|
are as accurate today as they were 100 years ago. Following
|
|
is an early account of its intoxicating properties made by
|
|
Dr. John Bell in 1857:
|
|
"I had taken the drug with great skepticism
|
|
as to its reputed action, or at any rate with the
|
|
opinion that it was grossly exaggerated, and I
|
|
accordingly made up my mind not to be 'caught
|
|
napping' in this way again, and to keep a careful
|
|
watch over my thoughts. But while enforcing this
|
|
resolution as I supposed, I found myself, to my
|
|
own astonishment, waking from a reverie longer and
|
|
more profound than any previous. From skepticism,
|
|
to the fullest belief of all I had read on the
|
|
subject, was but a step. Its effects so far
|
|
surpassed anything which words can convey, that I
|
|
began to think I was on the verge of narcotic
|
|
poisoning; yet, strange to say, there was not the
|
|
slightest feeling of inquietude on that account.
|
|
I resolved to walk into the street. While rising
|
|
from the chair, another lucid interval showed that
|
|
another dream had come and gone. While passing
|
|
through the door, I was aware of having wandered
|
|
again, but how or when I had permitted myself to
|
|
fall into the reverie I was perfectly unconscious,
|
|
and knew only that it seemed to have lasted an
|
|
interminable length of time." (Bell, 1857)
|
|
The user of cannabis feels the onset of the "high"
|
|
between 7 seconds (when smoking) and up to 30 minutes (after
|
|
eating). This involves a relaxed and peaceful, yet
|
|
sometimes euphoric state of mind. At high doses, it can
|
|
cause hallucinations. The effects last from 2 to 4 hours
|
|
after the drug is ingested, and it usually leaves the user
|
|
in a relaxed state for several hours after the high. One of
|
|
the main intoxicating properties is that short term memory
|
|
is inhibited for the duration of the high. Thoughts may
|
|
seem unclear, and it might be difficult for a user to
|
|
concentrate on logical-complicated concepts like
|
|
mathematics.
|
|
Long-term effects have been argued for many years. There
|
|
are claims of an "amotivational syndrome" where users are
|
|
said to withdraw from society and lose ambition. In
|
|
reviewing evidence for and against the theory of this
|
|
"syndrome," however, Marijuana and Health (Nat. Acad.
|
|
Sciences, Inst. Medicine, 1982) concluded that:
|
|
"Such symptoms have been known to occur in the
|
|
absence of marijuana. Even if there is an
|
|
association between this syndrome and the use of
|
|
marijuana, that does not prove that marijuana
|
|
causes the syndrome. Many troubled individuals
|
|
seek an 'escape' into use of drugs; thus, frequent
|
|
use of marijuana may become one more in a series
|
|
of counterproductive behaviors for these unhappy
|
|
people."
|
|
Other studies have found another interesting correlation:
|
|
Shedler et al. (1990) reported these results in a
|
|
longitudinal survey of adolescents:
|
|
"Adolescents who engaged in some drug
|
|
experimentation (primarily with marijuana) were
|
|
the best adjusted in the sample. Adolescents who
|
|
used drugs frequently were maladjusted, showing
|
|
distinct personality syndrome marked by
|
|
interpersonal alienation, poor impulse control,
|
|
and manifest emotional distress. Adolescents who,
|
|
by age 18, had never experimented with any drug
|
|
were relatively anxious, emotionally constricted,
|
|
and lacking in social skills."
|
|
Among other findings, Utah Power and Light spent $215.00 per
|
|
year less on health insurance benefits for drug users than
|
|
on the control group, and employees who tested positive for
|
|
cannabis at Georgia Power Co. had a higher promotion rate
|
|
than the company average, and were absent 30 percent less
|
|
(Morris, 1991).
|
|
|
|
Conclusion
|
|
|
|
Whether cannabis use causes permanent physical or
|
|
psychological changes in its users is still under question.
|
|
The most serious concern is its effects on the pulmonary
|
|
system, yet, studies have often used poor controls (i.e., no
|
|
filtration) and their results can mislead an uncareful
|
|
reader. Smoking the drug with a different apparatus or
|
|
ingesting it without smoking at all could greatly effect the
|
|
results of these studies.
|
|
The acute psychological effects of cannabis that cause
|
|
its intoxicating properties are no mystery, as any user can
|
|
report. Long term effects of cannabis use could possibly
|
|
lead to the so-called "amotivational syndrome," but
|
|
scientific evidence is lacking.
|
|
|
|
References Cited
|
|
|
|
Ames, B.N., Gold, L.S. Too many rodent carcinogens:
|
|
Mitogenesis increases mutagenesis. Science. Vol 149.
|
|
Pg. 971. 1990.
|
|
Bell, J. On the haschisch or cannabis indica. The Boston
|
|
Medical and Surgical Journal. Vol LVI, No. 11. April
|
|
16, 1857.
|
|
Cabral, G. et al. Chronic Marijuana Smoke Alters Alveolar
|
|
Macrophage Morphology and Protein Expression.
|
|
Fundamental and Applied Toxicolgy. 17:321-32. 1991.
|
|
Coggins, W.J., Swenson, E.W., Dawson, W.W., et al. Health
|
|
status of chronic heavy cannabis users. Ann. N.Y. Acad.
|
|
Sci. 282:148-161. 1976.
|
|
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.
|
|
Cohen, S. Therapeutic Aspects. Marijuana Research
|
|
Findings: 1980. NIDA Research Mongraph 31. 1980.
|
|
Glenn, Reed. Daily Camera. Jan. 2, 1992.
|
|
Harper, J.W., Heath, R.G., and Myers, W.A. Effects of
|
|
cannabis sativa on ultrastructure of the synapse in
|
|
monkey brain. J. Neurosci. Res. 3:87-93. 1977.
|
|
Heath, R.G., Fitzjarrell, A.T., Garey, R.E., and Myers, W.A.
|
|
Chronic marihuana smoking: Its effects on function and
|
|
structure of the primate brain. In Nahas, G.G. and
|
|
Paton, W.D.M. (eds) Marihuana: Biological Effects.
|
|
Analysis, Metabolism, Cullarlar Responses, Reproduction
|
|
and Brain. Pergamon Press: Oxford. 1979.
|
|
Heath, R.G., Fitzjarrell, A.T., Fontana, C.J., and Garey,
|
|
R.E. Cannabis sativa: Effects on brain function and
|
|
ultrastructure in Rhesus monkeys. Biological Pschiatry.
|
|
15:657-690. 1980.
|
|
Kolodny, R.C., Masters, W.H., Kolodner, R.M., and Toro, G.
|
|
Depression of plasma testosterone levels after chronic
|
|
intensive marijuana use. NEJM. 290:872-874. 1974.
|
|
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.
|
|
Landfield, P., Cadwallader, L. B., and Vinsant, S.
|
|
Quantitative changes in hippocampal structure following
|
|
long-term exposure to delta-9-tetrahydrocannabinol:
|
|
possible mediation by glucucorticoid systems. Brain
|
|
Research. Vol 443. 1988.
|
|
Mendelson, J.H., Kuehnle, J. Ellingboe, J., and Babor, T.F.
|
|
Plasma testosterone levels before, during, and after
|
|
chronic marihuana smoking. NEJM. 291:1051-1055. 1974.
|
|
Morris, D. Saint Paul Pioneer Press. May 6, 1991.
|
|
National Academy of Sciences, Institute of Medicine.
|
|
Marijuana and Health. National Academic Press:
|
|
Washington D.C. 1982.
|
|
NCRP Report #95. Radiation Exposure of the U.S. population
|
|
from consumer products and miscellaneous sources.
|
|
National Council on Radiation Protection and Measurement.
|
|
Dec 30, 1987.
|
|
Paule, M. et al. Chronic marijuana smoke exposure in the
|
|
rhesus monkey II: Effects on progressive ratio and
|
|
conditioned position responding. Journal of Pharmacology
|
|
and Experimental Therapeutics. 260: 210-22. 1992.
|
|
Shedler, J., Block, J. Adolescent drug use and
|
|
psychological health: A longitudinal inquiry. American
|
|
Psychologist. Vol 45(5) 612-630. 1990.
|
|
Tashkin, D.P., Fligiel S., Wu, T-C., Gong, H. Jr., Barbers,
|
|
R.G., Coulson, A.H., Simmons, M.S., Beals, T.F. Effects
|
|
of habitual use of marijuana and/or cocaine on the lung.
|
|
Research Findings on Smoking of Abused Substances. NIDA
|
|
Monograph 99. 1990.
|
|
Walton, R.P. Marihuana: America's New Drug Problem. J.B.
|
|
Lippincott: Philadelphia. 1874.
|
|
Winters, T.H., Franza, J.R. Radioactivity in Cigarette
|
|
Smoke. NEJM. 306(6): 364-365. 1982.
|
|
Wu, T-C., Tashkin, D.P., Djahed, B., and Rose, J.E.
|
|
Pulmonary hazards of smoking marijuana as compared with
|
|
tobacco. NEJM. 1988.
|
|
|
|
|
|
|