Misconceptions about cannabis

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Many misleading urban legends about cannabis exist. Like LSD rumors, many were spread during the 1960s and '70s, and are believed to continuously circulate today. These widespread legends claim that it is easy to overdose on the smokeable variant of cannabis and that it is extremely dangerous and addictive when compared to alcohol and tobacco chemicals, when in fact alcohol and the chemicals in tobacco, the drugs that are claimed to be safer, are actually considered by some psychiatrists specializing in the field of addictive behavior to be more addictive in comparison to cannabis.

This article's factual accuracy is disputed. Please help to ensure that disputed statements are reliably sourced. See the relevant discussion on the talk page. (January 2013) Withdrawal from heavy, chronic cannabis use does not usually exceed 3–4 days, but it has the potential to be psychologically addictive. Withdrawal symptoms are generally mild - loss of appetite, insomnia, feelings of uneasiness/anxiety, tension, stomach ache, headache and irritability all being common symptoms. There are studies that show no actual increased risk of cancer from smoking marijuana, even when duration of use is expanded over several years. In fact, some studies indicate THC to have anticancer properties, with studies showing tumor reduction in mice.

Confusion with Jimson weed

Historically, and possibly related to the "Reefer Madness" legend, some people (particularly Americans) had confused cannabis with Jimson weed (Datura stramonium). Jimson weed, which grows wild in the United States and several other countries, is a potent deliriant which can cause true hallucinations and delusions that are believed by the user to be real, as opposed to the pseudohallucinations and perceptual distortions typically caused by cannabis. Confusion could have resulted from the fact that datura's common name contains the word "weed," which is also a slang term for cannabis, and the fact that both plants (as well as others) have been given the moniker "loco weed" in the first half of the 20th century. Aside from these superficial similarities, the two plants are not related and have very little to do with one another, and thus should not be confused. Jimson weed is highly toxic and can cause delirium, confusion, hallucinations, blurred vision, photophobia, dry mouth, urinary retention, hyperthermia, incoordination, hypertension, and rapid heartbeat among other effects. An overdose (or suspected overdose) on this substance is a medical emergency, as it can cause seizures, coma, or death by cardiac arrest.

"Flashbacks" due to release from fat cells

Similar to one of the most enduring myths about LSD, and also somewhat related to the "multi-day impairment" legend described further down on this list, this legend claims that residual THC stored in fat cells gets released spontaneously into the bloodstream in enough quantities to get one high again long after the last use of cannabis, be it days, weeks, or even months later. This legend is typically accompanied by anecdotal evidence of people who experience a "high" after doing exercise of some sort. While somewhat more biologically plausible than the discredited LSD legend due to the fat-solubility of THC, this phenomenon remains scientifically unproven. A 2009 study of rats that involved injecting them with large quantities of THC (equivalent to 5-10 joints per day in humans) each day for ten days straight, then subjecting them to simulated severe stress or food deprivation led to double the blood levels of THC-COOH two days after the last THC exposure compared to rats that were neither stressed nor deprived of food. If such results occurred in humans, then it is theoretically possible for a chronic cannabis user to fail a drug test long after the usual detection time due to exercise, dieting, or severe stress shortly before the test—and several anecdotal reports of this exist. However, there is currently no hard evidence that enough active THC would be released to get one "high" or cause "flashbacks." One should also note that flashbacks from psychoactive drugs in general are now known to be psychological phenomena, and drug residues typically play no significant role in their occurrence and recurrence.

As for the anecdotes about exercise, they likely experienced a "runner's high" due to their bodies releasing endorphins, which are endogenous opioid agonists, along with anandamide and other endogenous cannabinoid agonists. These flashbacks have also been reported after one has stretched or stood up/sat or laid down abruptly. In addition, some studies find that the body produces endocannabinoids such as anandamide during exercise, which may also explain such effects since they activate the same receptors as THC.

George Washington smoked cannabis

There is a common belief that George Washington (and/or other Founding Fathers such as Thomas Jefferson) used cannabis for its psychoactive or medicinal properties. This has even made its way into popular films such as Dazed and Confused.

Both Washington and Jefferson grew cannabis to produce hemp, and Washington used hemp fiber to make clothes for his slaves, but there is no direct evidence that either Washington or Jefferson consumed it for its psychoactive properties. Washington is commonly quoted as saying "Make the most of the Indian hemp seed, and sow it everywhere," often cited as a note to his gardener published in The Washington Papers. However the closest phrase to this in The Washington Papers is in a letter to William Pearce – "I am very glad to hear that the Gardener has saved so much of the St. foin seed, and that of the India Hemp. Make the most you can of both, by sowing them again in drills. [...] The Hemp may be sown any where."

In The Papers of George Washington, "hemp" is defined as Cannabis sativa grown for fiber, and "Indian hemp" typically refers to the closely related Cannabis indica. While Washington was growing cannabis for its fiber, both of these species are also cultivated for their psychoactive and medicinal properties.

When cannabis is grown for its medicinal or psychoactive properties, male plants are routinely separated from females to prevent pollination, as non-pollinated female plants produce the most potent and prized flowering tops, known as sinsemilla (from the Spanish "sin semilla", meaning "without seed"). To produce sensimilla, the sexes must be separated before pollination occurs. On August 7, 1765, Washington wrote in his diary "Began to separate the Male from the Female hemp at Do.– rather too late." While this has been taken as evidence that Washington was growing cannabis for its psychoactive or medicinal properties, The Straight Dope points out that later entries in Washington's diary suggest that "he divided the plants because the males made stronger fiber while the female plants produced the seed needed for the next year's crop." Two days after he wrote the aforementioned entry in his diary, Washington wrote that he had "put some Hemp in the Rivr. to Rot," a technique used for producing hemp, not psychoactive cannabis. The following month he wrote that he "Began to Pull the Seed Hemp but it was not sufficiently ripe," and three weeks later that the "Hempseed seems to be in good order for getting – that is of a proper ripeness."

The introductory editorial for the June 2010 cannabinoid-themed issue of the British Journal of Pharmacology said that "there are sources that suggest that chronic tooth-ache may have led the first President of the United States, George Washington, to grow the plant for medicinal purposes," though these sources are not cited. The cover of the issue featured images of Washington and Queen Victoria placed on either side of a cannabis leaf.

Marijuana killed Bruce Lee

A number of rumours surfaced surrounding the cause of action film star Bruce Lee's death in 1973, one of which was that he had been killed by the consumption of cannabis. Lee died of a cerebral edema several hours after taking the painkiller and muscle relaxant equagesic. His autopsy showed trace amounts of cannabis in his stomach, and he had been known to use cannabis. However, a doctor at the coroner's hearing was quoted as saying that the cannabis in Lee's stomach was "no more significant than if Bruce had drunk a cup of tea that day."

Lee's physician, Donald Langford, and Peter Wu, a doctor who had treated Lee for another edema ten weeks earlier, believed that the fatal edema could have been caused by a rare allergic reaction to an alkaloid in cannabis, as a large quantity of hashish was removed from his stomach during the earlier edema, and he had been warned not to use it again. Wu told the coroner he believed the death was due to hypersensitivity to either cannabis or equagesic. However, Ronald D. Teare, a professor of forensic medicine at the University of London who was flown in to be the chief expert in the coroner's report, said that it was both "irresponsible and irrational" to attribute either edema to cannabis, and concluded the fatal edema was due to a rare reaction to equagesic. Teare, who had supervised nearly 100,000 autopsies and provided evidence for nearly 20,000 inquests in his 35 years of experience, was echoed by R. R. Lycette, the clinical pathologist at Queen Elizabeth Hospital. Lycette told the hearing that his death could not have been caused by cannabis, and that Lee had died from an edema caused by a reaction to one or both of the ingredients in equagesic.

At the time in Hong Kong, Cannabis was seen in an extremely negative light — worse than opium — and was "considered a 'foreign' drug with sinister and evil undertones." Bruce Thomas, author of Bruce Lee: Fighting Spirit stated that "this view had a massive impact on the official findings," and that Wu's inclusion of cannabis as a suspected cause of death "reflected this cultural and even political pressure." Wu later said in a 1992 interview with Thomas:

"Professor Teare was a forensic scientist recommended by Scotland Yard; he was brought in as the expert, so we can't contradict his testimony. The dosage of cannabis is neither precise nor predictable, but I've never known anyone to die simply from taking it."

Although it could not be completely ruled out that cannabis caused the edema, Teare's view was accepted by the coroner, and the official verdict was "death by misadventure" caused by a reaction to equigesic. Cannabis was not included as a possible cause of Lee's death.

Marijuana today is 10–20 times more potent than in the past

An oft-repeated legend is that today's cannabis is at least an order of magnitude stronger than in the past (and by implication much more dangerous). THC levels are allegedly 10, 20 or even 30 times higher than in the 1960s or 1970s. Although potency levels have risen in several countries (such as the US and UK), the actual increases have been much more modest (almost threefold from 1982 to 2007 in the US) and high-potency strains have always existed, as have various concentrated forms of cannabis. Furthermore, potency of seized samples was not tested before 1971, leaves were not distinguished from buds by testers at first, and samples from before the early 1980s (when testing and storage procedures were changed) were often degraded, making comparisons going that far back inaccurate. Non-representative sampling was also an issue. Since most of the increase happened after 2000, this legend can be considered an example of ostension (people have been making such claims as far back as the 1970s).

A related claim, especially in the UK, is that the cannabidiol/THC ratio has decreased over the past few decades, resulting in a new and presumably more dangerous form of cannabis that never existed before (since CBD is thought to attenuate some of the negative side effects of THC). While there is little to no reliable data before 2005 on such ratios in the UK, making comparisons to the past impossible, the US data going back to the 1970s shows little to no clear trend, and there have always been strains with extremely low ratios. Ratios are also known to vary widely between strains and growing/harvesting methods.

Some versions of this legend claim the potency change is due to "genetic modification," a term which often evokes fear in the popular consciousness, but there is no hard evidence that anything other than selective breeding and enhanced growing techniques are behind the change. "Genetic modification" insofar as attempting to emphasize desirable traits by the practice of selective breeding is standard practice across many areas of farming, including the production of cannabis. It is likely that the term "genetic modification" is used by people who do not understand that selective breeding is not the same as genetic engineering.

Multi-day impairment

Another claim about cannabis is that impairment due to smoking it lasts many days after using it, since THC is stored in the fat cells, leading to a low-grade haze long after the primary high is gone. This myth is based primarily on anecdotal evidence and the known fact that urine drug tests remain positive for at least several days after using, and longer for regular users. The tests however measure non-psychoactive metabolites, not active THC.[citation needed] And the blood levels of THC generally fall well below the psychoactive threshold within 2–4 hours of smoking (4–8 hours after oral use). A cannabis equivalent of a hangover may occur the morning after taking high doses, but even that ends much sooner than the legend suggests. While someone who smokes cannabis on Friday night would most likely come out positive in a urine test on Monday morning, he would no longer actually be impaired by that point.

One possible origin of this idea is the fact that some (but not all) studies with airline pilots have shown a modest decrease in capabilities on a flight simulator up to 24 hours after use of one fairly strong marijuana cigarette. In two of the four studies (one of which was not placebo-controlled) the ability of the pilots to safely navigate a simulated aircraft was apparently compromised somewhat up to 24 hours later, while the other two did not show any impairment beyond 4–8 hours. Despite the inconsistent replication, these studies have led some experts to recommend drug testing of people in safety-sensitive jobs (pilots, bus drivers, etc.). In contrast, no driving studies have found any significant cannabis-related impairments lasting beyond 2–6 hours.

It is also worth noting that the same research group that conducted three out of the four flight simulation studies on cannabis also conducted a similar study using alcohol. They found noticeable hangover-related impairment 14 hours after consuming enough alcohol to reach a BAC of 0.10, despite the fact that the BAC had returned to zero by that point.

Permanent memory loss or brain damage/destruction of brain cells

Another claim by many anti-drug organizations is that marijuana smoking causes permanent memory loss and/or brain damage. When told, it is often paired with anecdotal evidence about someone the teller supposedly knows of whose mind has become (presumably permanently) "fried" or "burnt" from it. While under the influence of cannabis, there is short-term memory loss but long term, persistent memory loss has not been found conclusively in any rigorous, carefully controlled scientific study. However, evidence of subtly altered brain structure in heavy users of marijuana does exist. The difficulty of determining damage due to heavy or chronic marijuana use in youth or adults arises because of covariants related to heavy marijuana use, including alcohol use or other drug use, making causality difficult to prove. Additionally, the politics and legal issues surrounding marijuana make detailed research difficult, and long-term funding unlikely, except in a very few cases.

Reefer madness

Originating in the 1930s, this myth was the basis for films like Reefer Madness, and used by Harry Anslinger of the Federal Bureau of Narcotics as justification for outlawing cannabis. The allegation was that even the calmest, most normal person could be transformed into a psychopathic killer or rapist solely from smoking a joint. No relationship has ever been proven linking such crimes to the acute intoxication of cannabis alone, and marijuana's psychological effects tend to be more associated with pacifism and inactivity than with aggression. For example, studies of the Jamaican working class showed no difference in the crime rates between users and the non-user of cannabis.

Smoking or chasing cannabis with tobacco increases the high

In many places, cannabis is routinely mixed with tobacco when rolled into joints. In North America cannabis in any form is also often "chased" with a tobacco cigarette, and hollowed-out cigars filled with cannabis (blunts) are also popular in some subcultures. Some users say that smoking tobacco increases the cannabis high, and this is often attributed to either the nicotine or additives such as menthol. Until recently this was based solely on anecdotal evidence. There may be at least some truth to this legend, as a 2005 study found that a transdermal nicotine patch modestly enhanced the subjective "high" of cannabis relative to a placebo patch—but only in males. Females actually saw a slight reduction in subjective effects.[70] Reasons for the enhancement are not well understood, and this study appears to be the only one as of 2010 that found such effects. However, another study found a significant downside to the practice. It appears that tobacco, which is known to be highly addictive, also enhances the likelihood of developing cannabis dependence symptoms when the two substances are used concurrently.

Some Lucky Strike cigarettes contained marijuana

It has been claimed the cigarette brand Lucky Strike is so named because every so often, a consumer of the product would have a "lucky strike," finding a marijuana spliff in a pack of cigarettes. The rumor varies in how often the marijuana cigarette would be included, anywhere from one in every thousand cartons to one in every pack. It's unclear when this myth originated; snopes.com claims it has been floating around for "many years." Lucky Strike's slogan "It's Toasted" fueled belief in the myth further ('toasted' being one slang term for being high on marijuana). Despite the popularity of the myth, there are no reliable reports of any Lucky Strike cigarette containing marijuana. The name "Lucky Strike," in reality, is only a marketing ploy, implying to customers that obtaining their brand is a "Lucky Strike." The "It's Toasted" slogan refers to the product's tobacco being toasted instead of sun-dried, making a supposedly better-tasting product.

Other urban legends offshoot from this one. One of the explanations for the origin of flipping a "lucky" cigarette upside down claims the practice originated from the Lucky Strike myth; it's presumed the superstition arose from flipping the marijuana-containing cigarette upside-down in order to save it for last.

Commercial marijuana cigarettes

A series of images has appeared and perpetuated over the internet implying the existence of marijuana-containing varieties of various major brands of cigarettes (most notably Camel and Marlboro), particularly 3-4 similar images of green and white Marlboro hard-pack boxes labeled either "Blend No. 420" or "Cannabis," containing either green-filtered or white-filtered cigarettes stamped with a green marijuana leaf logo. However, these are known to be no more than edited, manipulated, or otherwise altered images and are not actual existing products of these companies.

Popularity in the United States in the 1960s

Although the 1960s are often thought to have had rampant use of marijuana compared with the present day, in a 1969 Gallup poll only 4% of American adults had tried marijuana and 34% didn't know its effects. In contrast, later Gallup polls show that the percentage of adults who had tried marijuana had risen to 33% by 1985 and 34% by 1999.