Marijuana myths and facts
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.
THE FACTS:
The original basis of this claim was a report that, upon postmortem examinations, structural changes in several brain regions were found in two rhesus monkeys exposed to THC. Because these changes primarily involved the hippocampus, a cortical brain region known to play an important role in learning and memory, this finding suggested possible negative consequences for human marijuana users.
Additional studies, employing rodents, reported similar brain changes.
However, to achieve these results, massive doses of THC - up to 200 times the psychoactive dose in humans - had to be given . In fact, studies employing 100 times the human dose have failed to reveal any damage.
In the most recently published study, rhesus monkeys were exposed through face-mask inhalation to the smoke equivalent of four to five joints per day for one year. When sacrificed seven months later, there was no observed alteration of hippocampal architecture, cell size, cell number, or synaptic configuration. The authors conclude:
"while behavioral and neuroendocrinal effects are observed during marijuana smoke exposure in the monkey, residual neuropathological and neurochemical effects of marijuana exposure were not observed seven months after the year-long marijuana smoke regimen."
Thus, 20 years after the first report of brain damage in two marijuana-exposed monkeys, the claim of damage to brain cells has been effectively disproven.
No postmortem examinations of the brains of human marijuana users have ever been conducted. However, numerous studies have explored marijuana effect on brain-related cognitive functions. Many employ an experimental design - in which subjects are given marijuana in a laboratory setting, and then compared to controls on a variety of measures involving attention, learning and memory.
In a number of studies, no significant differences were detected. In fact, there is substantial research demonstrating that that marijuana intoxication does not impair the retrieval of information learned previously. However, there is evidence that marijuana, particularly in high doses, may interfere with users' ability to transfer new information into longterm memory.
While there is general agreement that, while under the influence of marijuana, learning is less efficient, there is no evidence that marijuana users - even longterm users - suffer permanent impairment. Indeed, numerous studies comparing chronic marijuana users with non-user controls have found no significant differences in learning, memory recall or other cognitive functions.
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.
THE FACTS:
There is no evidence that marijuana impairs male reproductive functioning.
The Jamaican and Costa Rican field studies detected no differences in hormone levels between marijuana users and non-users.
In epidemiological surveys of marijuana users, no problems with fertility have emerged as important.
In 1974, researchers reported diminished testosterone, reduced sexual function and abnormal sperm cells in males identified as chronic marijuana users. In a laboratory study, the same researchers reported an acute decrease in testosterone, but no chronic effect after nine weeks of smoking; they did not evaluate sperm volume or quality. In other laboratory studies, researchers have been generally unable to replicate these findings, although by administering very high THC doses - up to 20 cigarettes per day for 30 days - one study found a slight decrease in sperm concentrations. In all studies, test results remained within normal ranges and probably would not have affected actual fertility.
Severe adverse consequences have also been produced in male laboratory animals, although only with extremely high daily THC doses.
More importantly, in both the human and animal laboratory studies, all observed changes were reversed once THC administration was halted.
The claim that marijuana impairs female reproductive functioning in humans has no support in the scientific literature.
There have been no epidemiological studies indicating diminished fertility in female users of marijuana, and a recent survey found no impact of chronic marijuana use on female sex hormones.
Animal studies show hormonal changes and depressed ovulation following extremely high daily doses of THC. As occurs with males, these changes disappear once the experiment is completed. In addition, when THC was administered to female monkeys for an entire year, they developed tolerance to its hormonal effects and normal cycles were reestablished.
Almost immediately following publication of the few studies showing a marijuana impact on reproductive hormones, warnings about marijuana's potential impact on adolescent sexual development began to appear.
Other than one case report of a 16-year old marijuana smoker who had failed to progress to puberty, there has been nothing to indicate that such a potential exists. In whatever other ways one might consider marijuana to be bad for adolescents, it does not retard their sexual development.
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.
THE FACTS:
Most users of heroin, LSD and cocaine have used marijuana. However, most marijuana users never use another illegal drug.
Over time, there has been no consistent relationship between the use patterns of various drugs.
As marijuana use increased in the 1960s and 1970s, heroin use declined. And, when marijuana use declined in the 1980s, heroin use remained fairly stable.
For the past 20 years, as marijuana use-rates fluctuated, the use of LSD hardly changed at all.
Cocaine use increased in the early 1980s as marijuana use was declining. During the late 1980s, both marijuana and cocaine declined. During the last few years, cocaine use has continued to decline as marijuana use has increased slightly.
In 1994, less than 16% of high school seniors who had ever tried marijuana had ever tried cocaine - the lowest percentage ever recorded. In fact, as shown below, the proportion of marijuana users trying cocaine has declined steadily since 1986, when a high of more than 33% was recorded.
Proportion of Marijuana Users Ever Trying Cocaine
High School Seniors, 1975-1994
1975: 19% 1980: 27% 1985: 31% 1990: 22% 1976: 19% 1981: 28% 1986: 33% 1991: 22% 1977: 20% 1982: 27% 1987: 30% 1992: 18% 1978: 22% 1983: 28% 1988: 26% 1993: 17% 1979: 25% 1984: 29% 1989: 23% 1994: 16%
In short, there is no inevitable relationship between the use of marijuana and other drugs. This fact is supported by data from other countries. In the Netherlands, for example, although marijuana prevalence among young people increased during the past decade, cocaine use decreased - and remains considerably lower than in the United States. Whereas approximately 16% of youthful marijuana users in the U.S. have tried cocaine, the comparable figure for Dutch youth is 1.8 percent. Indeed, the Dutch policy of allowing marijuana to be purchased openly in government-regulated "coffee shops" was designed specifically to separate young marijuana users from illegal markets where heroin and cocaine are sold.
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.
THE FACTS:
The principal study fueling the original claim of immune impairment involved preparations created with white blood cells that had been removed from marijuana smokers and controls. After exposing the cells to known immune activators, researchers reported a lower rate of "transformation" in those taken from marijuana smokers.
However, numerous groups of scientists, using similar techniques, have failed to confirm this original study.
In fact, a 1988 study demonstrated an increase in responsiveness when white blood cells from marijuana smokers were exposed to immunological activators.
Studies involving laboratory animals have shown immune impairment following administration of THC, but only with the use of extremely high doses. For example, one study demonstrated an increase in herpes infection in rodents given doses of 100 mg/kg/day - a dose approximately 1000 times the dose necessary to produce a psychoactive effect in humans.
There have been no clinical or epidemiological studies showing an increase in bacterial, viral, or parasitic infection among human marijuana users. In three large field studies conducted in the 1970s, in Jamaica, Costa Rica and Greece, researchers found no differences in disease susceptibility between marijuana users and matched controls.
Marijuana use does not increase the risk of HIV infection; nor does it increase the onset or intensity of symptoms among AIDS patients. In fact, the FDA decision to approve the use of Marinol (synthetic THC) for use in HIV-wasting syndrome relied upon the absence of any immunopathology due to THC.
Thousands of people with AIDS are smoking marijuana daily to combat nausea and increase appetite. There is no scientific basis for claims that this practice compromises their immune responses. Indeed, the recent discovery of a peripheral cannabinoid receptor associated with lymphatic tissue should encourage aggressive exploration of THC's potential use as an immune-system stimulant.
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.
THE FACTS:
Except for their psychoactive ingredients, marijuana and tobacco smoke are nearly identical. Because most marijuana smokers inhale more deeply and hold the smoke in their lungs, more dangerous material may be consumed per cigarette. However, it is the total volume of irritant inhalation - not the amount in each cigarette - that matters.
Most tobacco smokers consume more than 10 cigarettes per day and some consume 40 or more. Regular marijuana smokers seldom consume more than three to five cigarettes per day and most consume far fewer. Thus, the amount of irritant material inhaled almost never approaches that of tobacco users.
Frequent marijuana smokers experience adverse respiratory symptoms from smoking, including chronic cough, chronic phlegm, and wheezing. However, the only prospective clinical study shows no increased risk of crippling pulmonary disease (chronic bronchitis and emphysema).
Since 1982, UCLA researchers have evaluated pulmonary function and bronchial cell characteristics in marijuana-only smokers, tobacco-only smokers, smokers of both, and non-smokers. Although they have found changes in marijuana-only smokers, the changes are much less pronounced than those found in tobacco smokers.
The nature of the marijuana-induced changes were also different, occurring primarily in the lung's large airways - not the small peripheral airways affected by tobacco smoke. Since it is small-airway inflammation that causes chronic bronchitis and emphysema, marijuana smokers may not develop these diseases.
In an epidemiological survey, approximately 1200 subjects gave information on smoking and pulmonary function at two-year intervals. A large percentage of the subjects underwent pulmonary function testing. Although a small group who reported previous marijuana smoking had significant pulmonary abnormalities, current marijuana smokers had no significant reduction in any pulmonary functions.
There are no epidemiological or aggregate clinical data suggesting that marijuana-only smokers develop lung cancer. However, since some bronchial cell changes appear to be pre-cancerous, an increased risk of cancer among frequent marijuana smokers is possible.
Since the pulmonary risks associated with marijuana are related to smoking, the danger is eliminated with other routes of administration. For committed smokers, pulmonary risk might be reduced with higher-potency products, which produce desired psychoactive effects with less inhalation of irritants. Smokers could also be encouraged to abandon deep inhalation and breath-holding, which increase drug delivery only slightly. Finally, pulmonary risk might be reduced if marijuana were smoked in water pipes rather than cigarettes.
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.
THE FACTS:
In high doses, marijuana probably produces driving impairment in most people. However, there is no evidence that marijuana, in current consumption patterns, contributes substantially to the rate of vehicular accidents in America.
A number of studies have looked for evidence of drugs in the blood or urine of drivers involved in fatal crashes. All have found alcohol present in 50% or more. Marijuana has been found much less often. Furthermore, in the majority of cases where marijuana has been detected, alcohol has been detected as well.
For example, a recent study sponsored by the U.S. National Highway Traffic Safety Administration (NHTSA) involving analysis of nearly 2000 fatal accident cases, found 6.7 % of drivers positive for marijuana. In more than two-thirds of those, alcohol was present and may have been the primary contributor to the fatal outcome.
To accurately assess marijuana's contribution to fatal crashes, the positive rate among deceased drivers would have to be compared to the positive rate from a random sample of drivers not involved in fatal accidents. Since the rate of past-month marijuana use for Americans above the legal driving age is about 12 percent, on any given day a substantial proportion of all drivers would test positive, particularly since marijuana s metabolites remain in blood and urine long after its psychoactive effects are finished.
A recent study found that one-third of those stopped for "reckless driving" between the hours of 7 p.m. and 2 a.m. - mostly young males - tested positive for marijuana (and no other drugs). To be meaningful, these test results would have to be compared to those from a matched control group of drivers.
A number of driving simulator studies have shown that marijuana does not produce the kind of psycho-motor impairment evident with modest doses of alcohol. In fact, in a recent NHTSA study, the only statistically significant outcome associated with marijuana was that drivers drove more slowly.
A recent study of actual driving ability under the influence of cannabis - employing the same protocol used to test the impairment-potential of medicinal drugs - evaluated the impact of placebo and three active THC doses in three driving trials, including one in high-density urban traffic.
Dose-related impairment was observed in drivers' ability to maintain steady lateral position. However, even with the highest dose of THC, impairment was relatively minor - comparable to that with blood-alcohol concentrations of between .03 and .07 % and many legal medications. Drivers under the influence of marijuana also tended to decrease their speed and approach other cars more cautiously.
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".
THE FACTS:
For more than 20 years the government-funded Potency Monitoring Project (PMP) at the University of Mississippi has been analyzing samples of marijuana submitted by U.S. law enforcement officials. At no time have police seizures reflected the marijuana generally available to users around the country and, in the 1970s, they were over- represented by large-volume low-potency Mexican kilobricks.
During the 1970s, the PMP regularly reported potency averages of under 1%, with a low of 0.4% in 1974. Quite clearly, these averages underestimate the THC content of marijuana smoked during this period.
Marijuana of under 0.5% potency has almost no psychoactivity. While it is possible that people sometimes obtained marijuana of such low potency, for the drug to have become popular in the 1960s and 1970s, most people must have regularly obtained marijuana with higher THC content.
Until the late 1970s, PMP samples included none of the traditionally higher-potency cannabis products, such as buds and sinsemilla, even though these products were available on the retail market. When changes in police practices resulted in their seizure, PMP potency averages increased.
Every independent analysis of potency in the 1970s found higher THC averages than the PMP. For example, the 59 samples submitted to PharmChem Laboratories in 1973 averaged 1.62%; only 16 (27%) contained less than 1% THC, more than half were over 2% and about one-fifth were over 4%. In 1975, PharmChem samples anged from 2 to 5%, with some as high as 14% - nearly 30 times the .71 average reported by the PMP.
After 1980, both the number and variety of official seizures increased dramatically, improving the validity of the PMP's reported averages, although they continue to be based on "convenience" rather than "representative" samples.
Even if potency had increased slightly since the 1970s, it would not mean that smoking marijuana had become more dangerous. In fact, since the primary health risk of marijuana comes from smoking, higher potency products can be less dangerous because they allow people to achieve the desired effect by inhaling less.
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. Marijuana is a drug without therapeutic value
Proposals to make marijuana legally available as a medicine are countered with claims that safer, more effective drugs are available, including a synthetic version of delta-9-THC, marijuana's primary active ingredient.
THE FACTS:
For thousands of years, throughout the world, people have used marijuana to treat a variety of medical conditions.
Today, in the United States, such use is prohibited. Although 36 states have passed legislation to allow marijuana's use as a medicine, federal law preempts their making marijuana legally available to patients.
A number of studies have shown that marijuana is effective in reducing nausea and vomiting, lowering intraocular pressure associated with glaucoma, and decreasing muscle spasm and spasticity. Today, many people use marijuana for these and other medical purposes, despite its illegal status.
People undergoing cancer chemotherapy have found smoked marijuana to be an effective anti-nauseant - often more effective than available pharmaceutical medications. Indeed, 44 % of oncologists responding to a questionnaire said they had recommended marijuana to their cancer patients; others said they would recommend it if it were legal.
Marijuana is also smoked by thousands of AIDS patients to treat the nausea and vomiting associated with both the disease and AZT drug therapy. Because it stimulates appetite, marijuana also counters HIV-related "wasting," allowing AIDS patients to gain weight and prolong their lives.
In 1986, a synthetic delta-9-THC capsule (Marinol) was marketed in the United States and labeled for use as an anti-emetic. Despite some utility, this product has serious drawbacks, including its cost. For example, a patient taking three five-milligram capsules a day would spend over $5,000 to use Marinol for one year. In comparison to the natural, smokeable product Marinol also has some pharmacological shortcomings.
Because THC delivered in oral capsules enters the bloodstream slowly, it yields lower scrum concentrations per dose.
Oral THC circulates in the body longer at effective concentrations, and more of it is metabolized to an active compound; thus, it more frequently yields unpleasant psychoactive effects.
In patients suffering from nausea, the swallowing of capsules may itself provoke vomiting.
In short, the smoking of crude marijuana is more efficient in delivering THC and, in some cases, it may be more effective.
The continuing illegality of medical marijuana is based more on political than scientific considerations. Although during the 1970s the government supported exploration into marijuana's therapeutic potential, its role has become one of blocking new research and opposing any change in marijuana's legal status.
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