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The Common Sense Series

a publication of the National Organization for the Reform of Marijuana Laws


The moderate use of marijuana is neither harmless nor devastating to the user. Unfortunately, the politics of marijuana has distorted research findings and made it difficult to find out the truth about marijuana's effect on human health. NORML believes that honest, verifiable information is the most effective tool to prevent the abuse of marijuana. This text examines the effects of marijuana on the human body, as described by a comprehensive report prepared for the Federal government by the most respected scientific body in the United States, the National Academy of Sciences. This text first examines some of the exaggerated claims made about marijuana and then provides the truth about marijuana's effects on human health.


Despite evidence to the contrary, many individuals and organizations maintain that marijuana is an extremely dangerous drug. For example, the National Federation of Parents for Drug Free Youth attempts to reach its societal and legislative goals by making the following claims:

  1. Marijuana is a harmful substance because it has 421 chemicals.
  2. Marijuana is stronger than it was 10 years ago, and this new, potent marijuana presents dangers unrecognized years ago.
  3. Marijuana is far worse for the lungs than tobacco.
  4. Marijuana causes damage to the reproductive system.
  5. The psychoactive chemicals in marijuana are fat soluble and stay in the human body for a month, increasing the danger of exposure.
  6. Marijuana causes brain damage and a behavioral disorder known as amotivational syndrome.
  7. Any use of marijuana is abuse, and marijuana has no medical value whatsoever.

The National Federation of Parents supports prohibition of marijuana because it believes that marijuana is so dangerous that no one can use it safely. According to the National Institute on Drug Abuse, which supports the NFP, many parents welcomed discovery of reports suggesting marijuana's harmfulness because the claims reinforced their own instincts about marijuana.

In fact, the reports used to justify the above claims have been found to be inconclusive by other researchers. Hence, warnings intended to dramatize the supposed ill-effects of marijuana are often couched with phrases like "marijuana can...". "Marijuana may...", or "If the experts are right...".


The Institute of Medicine of the National Academy of Sciences conducted a 15-month study of the health-related effects of marijuana in 1982. They appointed a 22-member committee to analyze existing scientific evidence bearing on the possible hazards to the health and safety of users of marijuana.

The report concludes: "the scientific evidence published to date indicates that marijuana has a broad range of psychological and biological effects, some of which, at least under certain circumstances, are harmful to human health".

In a companion report providing policy recommendations to the Academy's National Research Council, regulation of the marijuana market is advocated as the most effective method of controlling marijuana. The National Academy of Science's report rebuts many of the exaggerated claims made about marijuana.

  1. Of the 421 chemicals in marijuana, only 61 are unique to marijuana. The chemicals are known as cannabinoids. One of them, delta-9 THC, produces the psychoactive effect and is the focus of most research. The other 360 chemicals in the marijuana plant are found throughout other natural substances.
  2. The higher potency marijuana grown in the United States represents about half of all the marijuana consumed here. Because of it's higher potency many smokers use far less of it than less potent marijuana.
  3. Differences in dosage and frequency of consumption render comparisons between marijuana and tobacco consumption invalid, despite similarity in the composition of their smoke. Marijuana smoke irritates the lungs. Heavy exposure of the lungs to irritation such as smoke increases the likelihood of lung cancer and other lung problems. Marijuana speeds the heartbeat and is unhealthy for people with high blood pressure or other cardiovascular ailments.
  4. Marijuana does reduce the sperm count and obstruct sperm mobility in males within the normal range. These side-effects do not seem to affect human fertility, and are completely reversible thirty days after cessation of use. Marijuana, like other drugs, crosses the placenta. While the effects of this are unknown and there is no evidence that marijuana causes chromosome damage, we advise women to avoid the use of marijuana, tobacco, alcohol, or other drugs not prescribed by their physician during pregnancy and nursing.
  5. The intoxicating chemical, THC, is broken down by the human metabolism after two or three hours in the body. The by-products of this chemical breakdown are referred to as metabolites. These metabolites are fat soluble, and take 21-30 days to leave the human body via the urine. These metabolites exert no psychoactive effect on the human body.
  6. After reviewing all of the evidence, the Academy concluded: "There is not yet any conclusive evidence as to whether prolonged use of marijuana causes permanent changes in the nervous system or sustained impairment of brain function and behavior in human beings". "Interpretation of the evidence linking marijuana to 'amotivational syndrome' is difficult. 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 conterproductive behaviors for these unhappy people".
  7. "Cannabis and it's derivatives have shown promise in the treatment of a variety of disorders. The evidence is most impressive in glaucoma, where their mechanism of action appears to be different from standard drugs: in asthma.... and in the nausea and vomiting of cancer chemotherapy... Similar trials have suggested cannabis might also be used in seizures, spasticity, and other nervous system disorders".

N O R M L ' s V I E W

1. NORML favors discouraging marijuana abuse and is opposed to adolescent drug use.

2. Exaggerated claims about health hazards lack credibility and encourage adolescents to try marijuana and other drugs. Government research which relies on animal studies and studies of adolescent drug abusers presents a skewed perspective of marijuana's effects.

3. The illegality of marijuana, because it equates use with abuse, discourages frank discussion of marijuana's effects on health within the family and with doctors and nurses.

4. Over 35 million adult Americans use marijuana regularly because they find it a relatively safe way to relax. A regulated marijuana market would better protect their health than the unregulated black market.

W H A T D O Y O U T H I N K ?

For further information:


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