Many urban legends about illegal drugs have been created and circulated among children and the general public. These are commonly repeated by organizations which oppose all illegal drug use, often causing the true effects and dangers of drugs to be misunderstood and less scrutinized. The most common subjects of such legends are LSD, cannabis, and MDMA. These urban legends include misinformation about adulterants or other black market issues, as well as alleged effects of the pure substances.
A "bad trip" is easily caused by an expectation or fear of ill effects, which may later be blamed on "bad acid". While contamination is a concern in many illegal drugs, the extremely high potency of LSD relative to other drugs means that LSD doses are tiny, making it difficult to introduce a significant amount of a dangerous contaminant in a normal dose.
Analogs of LSD have little to no effect, even at high doses. Thus even these analogs are not a form of "bad acid".
One popular legend is the blue star tattoo legend. This legend frequently surfaces in American elementary and middle schools in the form of a flyer that has been photocopied through many generations, which is distributed to parents by concerned school officials. It has also become popular on Internet mailing lists and websites. This legend states that a temporary lick-and-stick tattoo soaked in LSD and made in the form of a blue star, or of popular children's cartoon characters, is being distributed to children in the area in order to get them addicted to LSD. The flyer lists an inaccurate description of the effects of LSD, some attribution (typically to a well-regarded hospital or a vaguely specified "adviser to the president"), and instructs parents to contact police if they come across the blue star tattoos. No actual cases of LSD distribution to children in this manner have ever been documented (also, LSD is not addictive and unlikely to be enjoyed by an unwitting user so there is no motivation for a dealer to do this).
A legend which falsely instills a fear of a non-existent effect of LSD is that the body stores crystallized LSD in spinal fluid or in fat cells, which at some point dislodges and causes horrific flashbacks, perhaps years later. Although the body does store some toxins in fat tissue, and residues of some drugs and toxins can be found in spinal fluid, LSD is not among these. LSD is metabolized by the liver, and has an elimination half-life of around 3–5 hours, and is insoluble in fats, being an alkaloid. This legend may have its foundation in the fact that chronic use can result in persistent psychosis and hallucinogenic persisting perception disorder (HPPD), so called “flashbacks."
Morning glory seeds, which are mildly hallucinogenic, are sometimes said to contain LSD. While they do contain the related chemical lysergic acid amide (LSA), this chemical is not particularly hallucinogenic in the quantities that morning glory seeds contain, but has been noted to be very hallucinogenic in hawaiian baby woodrose seeds. It is also difficult to convert to LSD.
Anti-drug educators frequently tell their students some variant on the theme of inevitable strychnine poisoning through LSD use, for example, that strychnine is commonly sold as a cheaper substitute for LSD by unscrupulous drug dealers; that strychnine is a byproduct of LSD synthesis; that the body produces strychnine as a result of LSD metabolism; or that strychnine is somehow necessary to bond LSD to blotter paper. None of this is true. These claims may even be believed and propagated by drug users themselves. In reality, most hallucinogens cause some degree of mental or physical discomfort after the "trip" is over. This is an indirect effect of the drug, not strychnine or any other adulterant. Additionally, strychnine itself is one of the most bitter substances known. The bitter taste can be detected at 1 part per million, which is well below the toxic level. Finally, the dangerous dose of strychnine is too high to be contained in a blotter square, even if the entire square were composed of the poison.
Strychnine has indeed rarely been discovered mixed with LSD and other drugs in a few samples recovered by law enforcement agencies, but these were all found in murder or attempted murder investigations where someone was being specifically targeted for poisoning, and not associated with recreational LSD use.
A related myth is that a new type of gang initiation requires the initiate to put a mixture of LSD and strychnine on the buttons of as many payphones as possible. This too, is debunked by the urban legends website Snopes.com.
The false claim states that it is possible to synthesize LSD or some similar hallucinogenic drug called "bananadine" from banana peels or other common household foods and chemicals. The actual synthesis of LSD usually requires advanced knowledge and experience in organic chemistry and requires both expensive laboratory equipment and expensive, carefully controlled precursor chemicals.
Originating from a recipe originally published as a hoax in the Berkeley Barb in March 1967, variants of this legend often circulate on the Internet and were popular on BBSs well before the widespread availability of Internet access through William Powell's "The Anarchist Cookbook". This book claimed "Musa Sapientum Bananadine" was a mild psychoactive drug found in banana peels. The slang terms "mellow yellow" and "saffron" (for the color of the peels) were borrowed from the 1966 Donovan song, "Mellow Yellow", perhaps because the phrase "electrical banana" is mentioned in one of the lines. According to The Rolling Stone Illustrated Encyclopedia of Rock and Roll, Donovan claimed he was actually referring to a banana-shaped vibrator. The song itself, despite its "psychedelic" feel, was written about Donovan's bout with hepatitis (which causes jaundice).
Many misleading urban legends about cannabis exist. Like LSD rumors, many were spread during the 1960s and 70's at the height of recreational drug use, 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 nicotine, when in fact alcohol and nicotine, the drugs that are claimed to be safer, are actually considered by many to be hard drugs in comparison to cannabis. Furthermore, scaling up from animal studies, an average human would need to ingest over a kilogram of cannabis to overdose.
Withdrawal from heavy, chronic cannabis use does not usually exceed 3–4 days (Though it may last as long as a month and a half in some), but it has the potential to be psychologically addictive, though this form of addiction tends to occur only after someone has been using the drug habitually. Withdrawal symptoms are generally mild, opposite the effects of use - loss of appetite/anorexia, 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 (this could be because THC allows cells to die faster). In fact, some studies indicate THC to have anticancer properties, with studies showing tumor reduction in mice.
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 (about twofold from 1982 to 2004 in the US) and high-potency strains have always existed. Furthermore, potency of seized samples was not tested for before 1971, and samples from before the early 1980s (when testing and storage procedures were changed) were often degraded, making comparisons going that far back inaccurate. Since most of the increase happened after 2000, this legend can be considered an example of ostentation (people have been making such claims as far back as the 1970s).
A long-standing myth against marijuana by many anti-drug groups is that its use eventually causes the user to seek a better high, or to "chase the first high", a term used to describe a drug addicts urge to achieve the same peak of euphoria they experienced on their first use. Studies in both the Netherlands, where the drug has been decriminalized for some time, and in the United States (in states where marijuana has been decriminalized) have shown that marijuana acts as a replacement for harder drugs (including alcohol, cocaine, and heroin) when it becomes easily and legally available. Emergency room visits (for harder drugs) decreased substantially in these locations following the decriminalization of marijuana.
Another claim by many anti-drug organizations is that marijuana smoking causes memory loss or damage. While intoxicated or 'high' 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 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 covariates related to heavy marijuana use, including alcohol use or other drug use. Additionally, the politics and legal issues surrounding marijuana make detailed research difficult, and long-term funding unlikely, except in very few cases.
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 non-users of cannabis.
Much street MDMA is actually deliberately impure (as opposed to being mis-sold as pure). While opinions vary on the allegation that ecstasy (MDMA) is often found on the street in an impure form, it is based on the fact that the majority of ecstasy pills tested in laboratories contain a mixture of several compounds: amphetamines, caffeine, DXM, dimenhydrinate (Dramamine), or other stimulants, anesthetics, dissociatives, and deliriants. It is believed these 'impurities' are actually added to enhance effect. Therefore, this makes the urban legend correct, but misunderstood.
A review of MDMA overdoses found that "most of the cases of serious toxicity or fatality have involved blood levels up to 40 times higher than the usual recreational range." 
Perhaps the best-known of the meth legends refers to people who heat/melt and then inhale crystal methamphetamine smoke. The legend states that the drug, once inhaled, will re-crystallize in large amounts inside the lungs, damaging them in the process. This is a false claim as street 'crystal' meth is usually in the form of methamphetamine hydrochloride, which is highly soluble in water and instantly gets absorbed into the user's blood stream via the alveoli.
However, intravenous methylphenidate (Ritalin) abuse results in a type of lung damage commonly known as "Ritalin Lung". Methylphenidate tablets are crushed and dissolved into solution for IV injection. The tablets contain talc and other particulates which can deposit in the lung (talcosis) and result in severe emphysema affecting all the lobes of the lung. The "Ritalin Lung" effect could be a possible source of how rumors about methamphetamine damaging the lungs could have surfaced.
Cotton fever is a high fever supposedly caused by injecting cotton fibers into the blood stream when shooting up heroin. Cotton is sometimes used as a crude filter for particulate matter prior to IV injection. Other commonly blamed substances include dirt if Mexican heroin was injected, or fiberglass if a cigarette filter was used (cigarette filters do not contain fiberglass). In general, cotton fever refers to a fever that users believe is caused by inanimate particulate matter injected into the blood stream. In reality, the particulate matter causing cotton fever is bacteria from lack of sterile technique. Most cases of cotton fever resolve as the body clears the infection. Users will often seek medical attention when cotton fever persists. Persistent cotton fever is often infective endocarditis. Although endotoxin shed by the bacteria Enterobacter agglomerans, which colonizes cotton plants, has been implicated as the cause of cotton fever, most clinical cases demonstrate blood cultures positive for skin and fecal bacteria.