There is a lot of defamation surrounding marijuana, such as the idea that it reduces intelligence. Despite the vast amount of research on the topic, in this article we examine some meta-analyses and twin studies to determine the potential causal relationship between cannabis use and IQ.
Cannabis carries numerous therapeutic advantages that can potentially alleviate various health conditions. If you have a medical condition treatable with cannabis and reside in the US, obtaining a medical marijuana card may be necessary to legally access it for medicinal use.
Cannabis has a long history of being associated with low IQ, and there is a widespread belief that it somehow reduces intelligence. The effects of cannabis on intelligence are still unknown, and the problem is extremely complicated. In addition, we still don’t fully understand what intelligence is. Studies are starting to show that while there may be a correlation between cannabis use and IQ, there may not be a causative one.
What Is IQ?
“Intelligence quotient,” or IQ for short, is a quantitative indicator of a person’s intelligence. Many people view it as a contentious measure, but more on that in a moment.
The renowned IQ test is used to determine IQ. The IQ test is available in numerous forms, some of which go by different names. But these days, they’re usually pretty standardized. They might assess verbal, logical, abstract, and general knowledge, among other things.
Most participants—roughly two thirds—will have an IQ of between 85 and 115. Roughly 2.5% will receive a score of 130 or lower.
What Insights Does IQ Provide?
IQ has been shown to be influenced by a wide range of variables, most of which do not directly provide information about the underlying processes of an individual’s brain but rather a multitude of interrelated physical and environmental factors. As such, it is far from being a pure measure of intelligence. Furthermore, it is very challenging to measure “intelligence” because it is an elusive concept in and of itself.
Tests of IQ can be useful in determining a restricted form of “academic intelligence,” but they don’t provide much information about creativity or social intelligence. As a result, even when we value IQ, we can still see our own prejudices against intelligence and the deeply held beliefs that surround it in our culture.
Furthermore, there is a strong correlation between environmental factors and the types of cognitive ability measured by IQ tests. This does not imply that they do not measure intelligence—intelligence is a sociobiological construct, after all—but rather that the measurement of intelligence carries and reinforces prejudices. For example, IQ tends to favor individuals similar to its creators, white men from the middle class.
Research indicates that racial group variances in mean scores are more likely to be caused by socioeconomic factors than by genetic factors. In fact, a quickening of the gap is unmistakable proof that environmental, as opposed to intrinsic, differences are the source of these findings. What can we infer from this? Because of this, IQ can be used to determine someone’s background in addition to intelligence.
Why Is This Important?
Understanding the history of IQ deficiencies is crucial because it could explain why there is a link between cannabis use and lower IQ. In short, using cannabis lowers one’s IQ. On closer examination, though, it seems that low IQ and cannabis use may have similar causes rather than one leading to the other.
Can Cannabis Use Impact IQ Levels?
It has long been believed that cannabis use, particularly in adolescence, lowers IQ over time. This theory is supported by numerous studies. But after some more investigation, it turns out that cannabis might not be the problem after all.
Scientific Proof: Cannabis Usage Does Not Result in Reduced IQ
There is mounting evidence that the reasons behind the reported IQ decline in cannabis users go back before cannabis use. Furthermore, it is believed that cannabis use shares these causes, which explains the strong correlation between what could be two effects of more elusive causes.
Twin studies are extremely helpful in determining the cause. Even though averages can be drawn from big populations, it can be challenging to apply these to a single person because you never know what that person would have looked like in any of their possible futures.
Since people X and Y are different, it’s difficult to say whether person X would have seen this decline had they never smoked. In the context of cannabis, it is possible to say that chronic smoker X has seen a two-point decline in IQ while non-smoker Y has not seen a decline.
Research involving identical twins helps to mitigate this issue because one of them can serve as the control group for the other. It is thought to be simpler to identify the reasons for differences between twins because of genetic similarities and similar upbringings (this is the most contentious aspect of twin studies—small differences can have big outcomes). In the instance of cannabis use, one could conclude that cannabis use lowers IQ if one twin who uses it has a lower IQ than the other who doesn’t, and this is seen across twin pairs.
Research indicates that this is untrue.
While cannabis use may be associated with a decline in IQ, a longitudinal study by Jackson et al., that included numerous twin pairs did not support this finding. There was no discernible IQ difference between twin pairs where one used cannabis during adolescence and the other did not at any point during the study.
They deduced from this that cannabis use was not the cause of the IQ point loss, but rather other variables like socioeconomic and family factors.
Similarly, similar results are shown by Meier et al. in another study. This study yielded three noteworthy discoveries. First, it was found that, by the time they started smoking cannabis at age 12, people who smoked had a lower IQ. Second, although their IQs did decline over the years that followed (during which they used cannabis), the decline was not larger than that noted in the individuals who abstained from cannabis use. Third, in twin pairs where one person used cannabis and the other did not, there was no discernible difference between the users and abstainers. They came to the same conclusion—that there were other causes for both cannabis addiction and a lower IQ.
It’s crucial to remember that neither of these studies came to the conclusion that cannabis smoking is caused by low IQ.
Final Verdict: The Relationship Between Cannabis and Intelligence
Research appears to indicate that environmental and socioeconomic factors contribute to both persistent cannabis use in adolescence and IQ decline, though more studies are needed in this area. Going back to the beginning, socioeconomic factors may account for the differences between cannabis users and non-users, just as they have been shown to be the cause of racial differences in IQ scores.
Having said that, we shouldn’t assume that cannabis use has no effect on IQ, particularly for those who use it while their brains are still growing. Even if there is no causal relationship between teenage use and IQ decline, it would be irrational to claim there isn’t one. As a result, we advise waiting to use cannabis until adulthood.