Does Cannabis Lower Your IQ?

The manner in which cannabis affects IQ has long been a hotly debated topic. Policymakers, parents, researchers, and, of course, the media, passionately (and empathically) weigh in on the debate. The debate often plays out in the press.
How many times have you seen headlines like this?

Pot Does Lower IQ, Study Finds

Or on the other side of the spectrum:

No, Marijuana Use Doesn’t Lower Your IQ

To understand how cannabis affects intelligence, it’s important to understand exactly how information gets processed in the brain. Basically, every time you have a thought, take a breath or experience a sensation, your brain is sending electrical signals from one neuron to the dendrite of another. Sometimes, the receiving neuron remains on and passes the message along to the next one and sometimes it turns off, takes a break, and the signal dyes. This happens to give the brain a chance to rest and focus on other areas as needed.

When THC gets involved, it interacts with this process, essentially hijacking the pathways and deciding for us what to focus on and what to ignore. When the pathways close, we lose track of our thoughts mid-sentence or have a hard time focusing in class, but when they stay open, they fire in all sorts of interesting ways! This out-of-the-box (“divergent”) thinking plays a key role in marijuana’s ability to promote creativity and is likely the reason so many successful people are daily cannabis consumers, as well.

A well-known 2012 study from New Zealand evaluated marijuana use and cognitive ability in more than 1,000 individuals over a 38-year period.

The researchers reported an association between ongoing marijuana use and cognitive decline.

In particular, they found that:

  • People who started using marijuana heavily as adolescents and continued as adults lost an average of six to eight IQ points by the time they reached midlife.
  • Among the group above, people who stopped using marijuana as adults didn’t regain lost IQ points.
  • People who started using marijuana heavily as adults didn’t experience any IQ loss.

This study had a significant impact for a few reasons.

First, it was among the first large, longitudinal (long-term) studies to assess marijuana use and cognitive functioning.

Next, the results suggest that marijuana use during adolescence may have an irreversible effect on adolescent brain development. Some additional research supports this conclusion.

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However, the New Zealand study also has significant limitations.

For one, it isn’t possible to conclude that marijuana use causes lower intelligence based on this study alone.

While the researchers controlled for differences in participant education levels, they didn’t rule out additional factors that may have contributed to cognitive decline.

A 2013 reply to the New Zealand study suggests that personality factors may play a role in both marijuana use and cognitive decline.

The author cited conscientiousness as an example. Low conscientiousness might explain both drug use and poor performance on tests of cognition.

Genetic factors may also contribute to cognitive decline, as suggested by a longitudinal twin study from 2016.

In this case, the researchers compared changes in IQ between twins who used marijuana and their abstinent siblings. They didn’t find any significant differences in IQ decline between the two groups.

The key takeaway? More research needs to be done to understand how marijuana use affects intelligence over time.

So, does cannabis affect IQ?

Unfortunately, there is no easy answer in the cannabis and IQ debate. Research suggests that there is something in the cannabis environment It is unclear whether this thing is cannabis itself, though the recent twin studies would suggest otherwise.

While many find that the herb enhances creativity and promotes focus, science has yet to catch up to subjective experience. The plant remains a popular muse among creative types, adding color to works of artistic genius.

Apart from the IQ question, research suggests that cannabis consumers may have hindered verbal memory than non-consumers. The study found that chronic cannabis consumers may lose as much as one word for every five years of heavy cannabis use.

On average, half of all cannabis consumers remembered one word less than their counterparts.

Does this mean that cannabis consumers are less intelligent? Certainly not. Perhaps it’s time to look at cannabis and intelligence in a more holistic way.

Professionals Proving You Can Get Stoned and Succeed

Anyone insisting cannabis causes laziness (or “amotivational syndrome” as some people call it) isn’t paying attention to the plethora of successful people who consume cannabis. People like Steve Jobs, Stephen King and even former president Barack Obama all admitted to consuming cannabis and have still made it to the top of their professions. Some creatives like Picasso, Shakespeare and the Beatles even credit sweet Mary Jane as the inspiration behind their success. And that’s not even to mention the whole industry founded by stoners who obviously have to be pretty intelligent to convince legislation to back us! Given its track record, it’s safe to assume cannabis use does not adversely affect intelligence or a person’s ability to succeed.

The notion that cannabis makes people dumb is an outdated concept that just won’t go away!

Though there is no solid evidence suggesting cannabis causes either an improvement or decline in cognitive ability, based on the trends we’ve seen, it’s quite possible cannabis may improve certain types of intelligence – ones that many employers find beneficial, no less. So the next time someone tells you pot makes people stupid, gather your thoughts, collect some research and prove them wrong!

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