3 Popular Myths About Cannabis Busted

When a plant has been banned for close to a century on the basis of almost no scientific evidence and then subjected to decades of often bizarre “public safety” campaigns, it’s bound to have a few dubious claims associated with it. This is certainly the case with cannabis, and separating marijuana fact from fiction can feel like a constant battle.

Thankfully, with cannabis legalization becoming more widespread and scientific research increasing, we can finally start putting some cannabis myths to rest.


Here’s a look at three especially popular cannabis tales—and why they’re completely wrong.

Myth #1: You’ll Get Higher if You Hold In Cannabis Smoke or Vapor

While many cannabis myths tend to originate from outside the cannabis community and are often of the alarmist Reefer Madness variety, this myth seems to be more popular among those who actually consume cannabis.

Intuitively, it does make sense to believe that holding in cannabis smoke before exhaling will make you feel higher. But is there any actual evidence to back up this claim?

Sadly, no.

One study looked at what effect breath-hold duration had on consumers’ experience with marijuana. Researchers analyzed participants depending on whether they held in their cannabis smoke for 0, 10 or 20 seconds on three separate occasions.

Researchers also measured:

  • Heart rate
  • Memory performance
  • Ratings of feeling high

They found that breath duration had no noticeable effect on any of the three measurements.

So, why is it that you may feel higher when you hold in a hit off a cannabis joint or vaporizer?

It probably has nothing to do with the cannabis itself. Instead, when you hold your breath in, you keep oxygen from flowing to your brain. This can cause you to feel lightheaded, which folks often mistake for an enhanced high.

Myth #2: Smoking Cannabis Kills Brain Cells

The stereotype of the half-baked stoner is probably why a lot of people think that marijuana must be bad for the brain. While it’s true that getting high does decrease short-term memory temporarily, the notion that it kills brain cells is a complete myth.


One 2016 study by researchers at Duke University analyzed two identical twins—one who consumed cannabis and the other who didn’t—for a decade. The results showed that both twins had almost the exact same level of cognitive functioning after 10 years.

Likewise, a 2015 University of Colorado study used functional MRI machines to analyze the brains of both cannabis consumers and non-consumers. The researchers looked for differences in their brains’:

  • Size
  • Structure
  • Shape

Again, the results showed no differences between the cannabis group and the non-cannabis group.

People who insist marijuana damages brain cells often point to a study from the 1970s by Dr. Robert Heath of Tulane University. His study claimed that rhesus monkeys exposed to cannabis smoke exhibited brain damage.

However, this study was almost ludicrously flawed and has since been thoroughly debunked. For one, Dr. Heath didn’t publish his study methods, only the results. This, of course, made it impossible to replicate and verify the results.

When his methods were finally revealed, it turned out that Dr. Heath was actually pumping the equivalent of 250 cannabis joints of smoke into the monkeys’ cages each day.

That Dr. Heath’s methods were completely bogus and unethical shouldn’t come as a surprise when you learn a little about him. By the time he’d conducted his cannabis “research,” he’d already built a career performing a lot of unethical tests. These included:

  • Testing “brainwashing” drugs on prisoners for the CIA
  • Implanting electrodes into women’s brains to cure their “frigidity”
  • Using electrodes on gay men in an early and particularly brutal form of conversion therapy

In other words, he wasn’t exactly the sort of person you’d trust to develop reliable, scientific data about cannabis.

In fact, not only was Dr. Heath’s research completely bogus, but it turns out cannabis actually has a number of benefits that support brain health, including in the battle against dementia and traumatic brain injuries.


Myth #3: You Can Get a Contact High Off of Second-Hand Cannabis Smoke

Imagine you’re sitting in a room full of people smoking cannabis, but the next day you have to pass a drug test for a new job. Should you be worried about getting high—also called a contact high—and failing your drug test? The answer is: probably not.

While theoretically possible, to get high off of second-hand cannabis smoke, you’d have to be around a lot of it, preferably in a small, unventilated room for hours on end. And even then, you’d probably still pass your drug test.

One study tested the THC levels of non-cannabis consumers after they spent time sitting in both nonventilated and ventilated rooms with people smoking cannabis. The results showed that while the non-cannabis consumers did have trace amounts of THC in their systems, the levels were so low that they would have had no trouble passing a drug test.


While THC amounts were slightly higher for the participants in the nonventilated room, they were still low. So, while under extreme circumstances this myth could be true, you’d have to go to pretty great lengths to make it happen.

Photo credit: Couperfield/

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