In 2012, a man named Rudy Eugene blemished the good reputation of Florida when he leapt upon a stranger in Miami and began chewing on his face before being shot and killed by responding officers.

Headlines everywhere speculated that Eugene developed this spontaneous taste for human flesh because he had ingested bath salts, the slang term for a group of recreational synthetic drugs that were rumored to cause bizarre behavior and psychosis. He was dubbed the Causeway Cannibal.

Then the toxicology report came back. Eugene didn’t have any bath salts in his system. No LSD, no PCP, no Ecstasy or heroin or even baby aspirin.

The only mind-altering substance found was … marijuana. Which can make you hungry, but not usually for human flesh. To this day, though, many people believe bath salts are synonymous with cannibalism.

It’s just one of the many misunderstandings about drugs—both legal and otherwise—we’ll be passing around on this installment of Misconceptions. Hi, I’m Justin Dodd and like you, I’ve heard a number of common misconceptions about various recreational, legal, and illegal substances. While we’ll be discussing some today, we want to stress that we in no way condone the use of any drug and are absolutely not advising viewers on how best to administer these or any substances.

That should be left to medical professionals, and although there probably isn’t any confusion on this front, I am not one of them. Good? Good.

Let’s get started. Misconception: Study Drugs Make You Smarter If you’ve ever faced a long night of cramming for a test you forgot you had, you’ve probably heard of so-called study drugs like Adderall or Ritalin. These prescription stimulants—which are intended to treat actual medical conditions, like Attention-Deficit / Hyperactivity Disorder—have a very off-label reputation for increasing alertness and sharpening focus so you can get that 30-page term paper written in under an hour while also sketching a simple formula for nuclear fusion.

But students who do not have ADHD who take stimulant drugs intended to treat ADHD are probably not helping their mental acuity. They might even be harming it. A 2016 study summary published in the Experimental and Clinical Psychopharmacology science journal found that no mental functions involving decision-making, memory, or verbal fluency were positively impacted by the drugs.

They concluded that: “In contrast, preliminary findings, although limited by a small number of studies, generally do not support significant effects of prescription stimulants on various behavioral measures of attention, executive function (e.g., decision making, verbal fluency, and planning), reversal learning, or cognitive flexibility. The mechanisms explaining neurocognitive enhancement, however, are less understood. For example, it is possible that neuroenhancement is better explained by placebo effects, altered perception of quality of work, or enhanced energy and motivation to improve productivity.” Researchers believe that off-label users conflate the energy burst they get from the drugs with cognitive improvement.

Another study found that subjects taking Adderall performed no better in reading comprehension than those getting a placebo. They actually performed worse in a working memory test. Such medication can improve academic performance for people with ADHD—you know, people for whom the drug is actually prescribed.

The estimated 17 percent of college students who misuse them, though, should especially take heed of their possible adverse effects. Everything from sleep issues to drug interactions to dependency are all possible on stimulant drugs. All of those things are absolutely not benefits when it comes to aiming for a 4.0 GPA.

Now, it is true that stimulants can certainly provide an energy boost and a kind of neuroenhancement, but so can coffee. So maybe try that as a study aid instead. And speaking of the country’s most widely-embraced drug: Caffeine.

It’s a drug in every sense, yet we generally don’t think twice about ingesting it. The CDC says that around 80 percent of American adults consume caffeine daily. As discussed in our recent Food History episode about coffee and tea, caffeine works by jamming up the adenosine receptors, docking in them and blocking adenosine from entering.

Adenosine is a neurotransmitter produced by your body to tell you you’re getting sleepy. Thanks to caffeine, that message gets passed to your body’s spam folder. That allows dopamine to run wild, at least until the caffeine wears off, at which point you might feel like a clock in a Salvador Dalí painting.

Ya know, goopy. Caffeine might give you the jitters or a headache. But it won’t dehydrate you.

Caffeine is a very mild diuretic, meaning it can increase the need to urinate. Some people observe that phenomenon and assume that caffeine must be draining your body of every precious ounce of fluid. Even health experts have recommended limiting caffeine intake or drinking more water to compensate for how it will supposedly leave you feeling like a wrung-out sponge.

But science hasn’t been able to back that fear up. Studies have been done looking at mild to moderate caffeine intake against hydration tests in subjects. Basically, people have chugged coffee and then had their body fluid levels tested to see if they were at risk of dehydration.

There are usually no statistically significant differences found in the hydration levels of people drinking coffee over those drinking water. Both liquids were hydrating. When it comes to the biggest misconception about coffee, it might be a tie between thinking it will dry you out and thinking it will sober you up.

Several studies have looked at whether caffeine can cancel out the effects of alcohol and the results are mixed at best. Mice who were given alcohol and then the human equivalent of eight cups of coffee were still much worse at getting around a maze than teetotaling mice. Caffeine can make you more alert and offset some of the drowsiness brought on by alcohol, but it can’t actually make you less inebriated.

In fact, hitting the bottle and then the coffee pot might actually delude you into believing you’re less intoxicated than you really are, just because you have a little more energy. That can obviously be pretty dangerous. If you’ve ever heard a story about a criminal suspect who was all but impossible to subdue during an arrest, the term PCP may have come up.

This street drug, also known as phencyclidine or angel dust, grew in popularity in the 1970s. And with that increased prevalence came reports that it could render users almost impervious to pain and arm them with incredible strength—enough to snap out of handcuffs or tackle multiple police officers at a time. It was kind of like a super soldier serum you could buy from a guy lurking in an alley.

Alas, PCP never had a place in the Marvel Cinematic Universe, though it did pop up in one episode of Buffy the Vampire Slayer as a possible cover story for some undead carnage. The drug can numb some pain—it was originally designed as surgical anesthetic, in fact—but it doesn’t make users invulnerable and it never gave anyone the ability to punch through walls. Instead, many pharmacologists and sociologists believed the drug was an example of how law enforcement could demonize a drug in order to justify the use of excessive force.

A similar dynamic had transpired with cocaine at the turn of the 20th century, when a rumor spread that it could actually render people resistant to .32 caliber bullets. In the South, that supposedly morphed into a belief that police officers needed .38 caliber bullets in order to defend themselves against a cocaine user. One New York Times article from 1914 perpetuated the myth, saying that cocaine offered: “...a resistance to the ‘knock down’ effects of fatal wounds.

Bullets fired into vital parts, that would drop a sane man in his tracks, fail to check the [cocaine] ‘fiend.’” That is … not supported by science, to say the least. These kinds of scare tactics might seem almost comically overwrought to us today, but there’s a good argument to be made that this kind of reporting helped facilitate and excuse police brutality and racist assumptions about suspects. The specious argument linking drugs and super strength resurfaced in 1991, when the Los Angeles Police Department asserted that beating victim Rodney King had posed a danger to officers because he was suspected of being on PCP.

For what it’s worth, a drug screen found no PCP in King’s system. The truth is that while there were some cases of civilians behaving aggressively while on the drug, the vast majority could not and did not break their handcuffs or descend into hallucinations. According to TIME Magazine, “the single study done on the subject [of PCP and muscle power] in mice found a drop in grip strength among animals given the drug.” And now my mind is trying to figure out how you get mice to use hand-grippers.

Anyway. There’s never been any evidence that PCP could improve strength, in fact, though you can count on it to impair memory, induce seizures, and provoke fatal reactions, especially when interacting with other drugs. Fortunately, PCP use declined rapidly in the 1990s, though it continues to plague some communities.

If police do encounter someone on the drug, a standard pair of handcuffs would be sufficient. Lysergic acid diethylamide sounds like an oven cleaner. It’s actually the chemical name of LSD, the synthetic drug with psychedelic properties that pulls users into a trip.

With the rise of LSD in the 1960s came the belief that users might experience flashbacks, or spontaneous acid trips that cropped up long after the drug had been taken. One possible explanation was that LSD molecules might hang out in the spinal cord, only to be released at unexpected times. It’s like the scarier version of the seven-years-to-digest-gum myth, and it was cited as yet another reason to avoid the mind-altering drug.

Misconceptions like this helped sideline research into whether hallucinogens could have benefits in psychotherapy—research which has only recently begun to pick up steam again. LSD does not attach itself to your spine. And flashbacks, while handy for comedies set in the 1960s, are very rare, and not so comical.

They’re called Hallucinogen Persisting Perception Disorder, or HPPD, and it’s more of a perpetual visual disturbance than a spontaneous repeat of an acid trip. They’re not always brought on by LSD, in fact—any hallucinogen can lead to HPPD. It’s even been seen, albeit extremely rarely, amongst cannabis users.

HPPD sufferers are said to see things like geometric shapes and flashes of color that can last years. So what should we make of so-called flashbacks? The could be simply a recollection of a past drug experience or a psychiatric condition that is being falsely attributed to past drug use.

Marijuana has long been labeled a gateway drug, meaning that those who toke are more likely to graduate to serious and dangerous drugs. This theory does not hold bong water. No study has ever demonstrated a causal relationship between marijuana use and moving on to hard drugs.

Some research has noted that hard drug users had smoked pot in the past, but this only shows correlation—not cause and effect. What’s likely happening is that someone who has a predisposition to try a drug will also have a willingness to try other drugs. In other words, the desire was there prior to marijuana—or at the very least, the same circumstances that led them to seek out one mind-altering substance could have led them to seek out another.

Describing marijuana as a gateway drug is like calling alcohol a gateway drug to weed. Plenty of people have had a beer before smoking a joint, but consuming a Bud Light is not a risk factor for becoming a fan of jam bands. I’m looking at you Deadheads.

There is scientific evidence that THC, the active ingredient in marijuana, may prime the brain to be more receptive to other drugs in the future, which is called cross-sensitization. But that doesn’t demonstrate a firm or unique relationship between marijuana consumption and harder drug use. Even the total squares at the National Institutes of Health say that: “…the majority of people who use marijuana do not go on to use other, ‘harder’ substances.

Also, cross-sensitization is not unique to marijuana. Alcohol and nicotine also prime the brain for a heightened response to other drugs and are, like marijuana, also typically used before a person progresses to other, more harmful substances.” In the past, marijuana may have opened doors in a more literal sense, since scoring a bag from some sketchy random could conceivably grant you access to people who had more serious inventory. But with the increasing legalization of marijuana, even that flimsy justification for calling it a gateway substance is fading fast.

That’s not to say marijuana use is completely harmless. And yes, we know you’re groaning at how out of touch I seem, but the reality is marijuana can cause impaired body movement and impaired memory as well as lung irritation. According to the National Institute on Drug Abuse, those who begin using marijuana as teenagers could potentially see their cognitive development affected, though researchers aren’t yet sure how environmental factors or genetics can influence that.

Everyone knows that a police officer can conduct a Breathalyzer exam to check if someone is drunk. That data is actually more controversial than you might realize, but it is, at minimum, a way for law enforcement to establish probable cause before conducting a more reliable test for blood alcohol level. But it’s more difficult to assess whether someone is under the influence of other drugs, whether it’s marijuana, prescription, or illegal drugs—what some have dubbed drugged, rather than drunk, driving.

But difficult doesn’t mean impossible. Protocol varies from state to state, but some police departments are making use of drug recognition experts, or DREs, who have received training to evaluate whether someone might be in an altered state of consciousness after being pulled over. In addition to the standard tests, like asking someone to touch the tip of their nose with their finger or perform balance exercises, these officers also check vital signs, interview the subject and officers on the scene, and even supervise urine or blood work that can detect drugs.

Colorado and Illinois, for example, have set a THC limit of 5 nanograms per milliliter of blood, while other states have strict zero-tolerance laws for driving with THC in the system. Now, this does get tricky, because THC can be detected in the body even after its cognitive effects have worn off—even for weeks. A cop could stop you, administer a blood test at a hospital, and determine you’re over the limit.

But how do they know that wasn’t the result of something you took days ago? That’s still being worked out. In Illinois, for example, signs of impairment can result in a quick mouth swab that tests for recently consumed THC.

A positive test might be probable cause for an arrest. And while an officer can’t say what specific drug is being used without lab tests, they can make general observations. Looking at things like pupil dilation and body temperature, an officer might conclude that someone is on painkillers, for example.

Prescribed or not, it’s illegal to drive under the influence. Bear in mind this kind of on-site evaluation or drug tests are highly controversial. A DRE officer is making a subjective observation of someone under the influence, which can be challenged by defense attorneys.

And the drug kits used to identify drugs found in cars can and have produced false positives. So we’re not saying these tests are irrefutable, just that police departments are making use of them, and drugged driving is not something you’re likely to get away with—nor, do I have to say it?—should you try to. Which brings us to our final point: When that prescription pill bottle tells you not to operate heavy machinery, they don’t just mean construction equipment.

They also mean your Honda. That’s it for this episode of Misconceptions. Of course, we don’t want to minimize the possible effects of drug use, which really can have a devastating impact on individuals and communities.

Hopefully, though, putting more accurate and even-handed information out there is a positive, if small, contribution to our corner of the Internet. Thanks for watching. We’ll see you next time.