New Twin Study Confirms That Cannabis Does Not Lower IQ

Denys Svirepchuk
Denys Svirepchuk

Denys Svirepchuk is a dynamic writer at AskGrowers known for his engaging and informative content. His articles often blend entertainment with education, offering readers a unique perspective on the cannabis industry. Denys is particularly adept at crafting content that ranges from fun and quirky ideas, like cannabis-themed gifts to more serious topics such as industry news and legalization updates. He also provides in articles valuable guides and lifehacks for cannabis enthusiasts, delving into the specifics of cannabinoids and other intricate aspects of cannabis. Denys' work is characterized by its diversity making him a versatile and much-appreciated contributor to the cannabis community.

Reviewed by Helga Green



8 min
Find more about Denys
New Twin Study Confirms That Cannabis Does Not Lower IQ

Marijuana was forbidden and stigmatized throughout the 20th century, but now, it seems that the public opinion on weed is swaying towards being more favorable. Nonetheless, the debate over the effects of long-term marijuana use and its possible effects on the human brain and body is still on. There are lots of myths and stereotypes related to marijuana — some people still think of it as a gateway drug or that marijuana lowers IQ.

The IQ thing is one of the popular stereotypes around cannabis. Many people ask: does marijuana lower IQ or make you dumber? Until recently, there was not enough scientific evidence to either prove or debunk that idea — but now, we finally know the truth. The latest twin study debunked the stereotype, so now we can safely say that cannabis doesn’t lead to an IQ drop. Want to know more? Then continue reading!

Details of the Cannabis IQ Drop Twin Study

In 2012, 10 professors from the United States, the United Kingdom, and New Zealand published the study on the subject matter. This study showed the neuropsychological decline in persistent cannabis users. This was a prospective study of a birth cohort of 1,037 people followed from birth to age 38. The authors of the research paper tested neuropsychological functioning at ages 13 and 38. The researchers found that cannabis users had worse cognitive performance and that the more marijuana they used, the lower scores they had.

But the latest study, published in 2019, contradicts the results of the previous one. 7 scientists from the United States published a paper that is based on data from twins from the United Kingdom. This paper expands the previous studies in several ways to understand if it’s really marijuana that leads to lower scores on cognitive tests or something else; something that the previous researchers may have missed. To have better control of all the factors, the authors of the 2019 paper choose twins as their research group — the thing is that twins provide a very valuable source of data for both health and psychological research, which gives the scientists the opportunity to pull apart and examine the genetic and environmental influences. That’s why twin studies are more reliable, and that’s why the 2019 study looks more credible when talking about the marijuana effects on brain and cognitive functions. So, what does the new study imply for our understanding of the long-term effects of cannabis?

The Effects of Marijuana on the Brain

In simple terms, look at your average college – some students demonstrate some substantial academic achievements, and the others perform poorly, but it doesn’t have anything to do with marijuana use. It’s a huge combination of factors that contributes to their academic achievements; such factors as genetic influences and (or) environmental issues are the real reasons why some students have better cognitive functions than others. They found very little support for a causal effect of weed use on cognition (only 1 within-family test out of 428), which means that basically, marijuana does not cause a decline in cognitive ability.

There was another study published in 2014 by the London researchers. According to this one, even heavy marijuana use didn’t lower the IQ of the teenagers who were examined. More than 2,600 children were examined at age 8 and at age 15; and according to this study, there is NO relationship between cannabis use and lower IQ. The authors paid more attention to the confounding factors, such as alcohol/tobacco use and maternal education (factors the authors of the 2012 study dismissed), and what they found is that it’s alcohol use that can be associated with the IQ decline, not cannabis use.

Yet another study, published in the PNAS scientific journal in 2016, says that there is no direct link between the use of marijuana and IQ test scores. The main idea of this study, as well as the 2019 study, is that the IQ decline was previously mistakenly associated with cannabis use because it’s linked to other substance use, such as alcohol, and it’s these “other substances” that drive the IQ decline, not marijuana itself. Naturally, there can be a variety of factors contributing to the decline of IQ in teens and adults – stress, environment, alcohol abuse, tobacco, and even aging. All of these piled up can create a substantial difference in IQ test results over a long period of time.

Is Cannabis That Harmless?

But here’s another thing you should know: marijuana is not really that harmless. For instance, marijuana can affect the cognitive functions of some students, and it can lead to reduced educational performance in 12th graders — but it’s not about their IQ going down. Such factors as laziness and lack of motivation are the main contributing factors to that decline in academic performance. The cognitive functions of the students were not affected by the marijuana use, just the motivation to study. Some people do also get bad trips after smoking weed or eating edibles — sweating, shortness of breath, pale look, and other symptoms can happen because of several reasons, from uncomfortable settings to music you’re listening to. Well, to be fair, bad trips can easily be prevented and stopped — just eat or drink something sweet and think about something nice, it usually helps.

This plant can impair your judgment and coordination, which, in turn, can lead to drowsiness and distraction. It can affect driving, and it can make you feel bad and sometimes even depressed. But, paraphrasing Churchill, it’s the worst recreational drug except for all the rest. So, talking about the long-term effects of weed, we have one down – the weed does not influence your IQ. Of course, the choice to smoke weed or not is yours to make, and we want you to make the decisions on your own. If you are an adult, you have to have the right to decide what to do with your consciousness and which substances to use. A moderate, and let me stress it once again, moderate use of marijuana will not affect your cognitive capabilities or make you dumb.

Cannabidiol Products for Stress and Anxiety

Of course, you need to consider such factors as your own health and predispositions. For instance, people who have a history of schizophrenia running in their family might be better off staying clear of psychoactive substances. If you suffer from stress and anxiety disorder, you might also want to avoid weed, especially one that’s potent in THC because of the possible paranoia attacks. It is true that the high content of THC in weed can produce detrimental effects upon individuals inclined towards mental issues like stress disorder, anxiety disorder, or schizophrenia. On the other hand, the CBD component in cannabis has been proven to reduce stress and anxiety, which is why so many people, including medical professionals, recommend cannabidiol products as one of the possible remedies for such diseases.

There’s another curious study from 2021 that actually speaks in favor of those claiming weed to be the reason why people get dumber. The research conducted at RCSI University of Medicine shows that there might actually be a correlation between frequent marijuana use and IQ drop. The study with a focus group of more than 6000 young adults has shown that those who smoke weed weekly lost 2 IQ points over the span of 6 months. Of course, we are talking about a completely random group of people whose IQ score might have been influenced by a wide variety of factors starting with stress and ending with environmental issues. Again, we can’t be sure weed was the reason those people lost their 2 IQ points over that period of time as there could have been a whole bunch of reasons for why those results have occurred.

Read Also: Does CBD Affect the Brain and Memory?

Wrap Up

To give this topic closure, weed is a relatively safe substance, especially when you know what you are doing. Just consider all the pros and cons for yourself and make a reasonable decision. The moderate use of marijuana has its benefits, and irresponsible consumption of weed might have its detriments. You need to remember that and make a decision that is best for you. With that in mind, you can be sure that moderate consumption of marijuana will not make you stupid and influence your cognitive capacity in any way. However, the case is not closed, new studies come every year, and though most of those speak in favor of weed, others still show some controversial results. Once again, moderation is the key to success if you want to lead a healthy life full of vivid experiences and smoke your pot from time to time.


No reviews yet...
Be the first and share your opinion

Write a Review

Related articles

Top articles

Recent Articles