Does Cannabis Reduce IQ Levels And Problems With Education?

Does Cannabis Reduce IQ Levels And Problems With Education?

The claim that regular use of marijuana reduces Intelligence Quotient (IQ) and causes difficulties in learning is just a propaganda often cited by marijuana opponents. However, what do the scientists got to say about this statement?

Research studies: cannabis does not reduce IQ

According to a study published in the international scientific journal “The Journal of Psychopharmacology” — The use of marijuana among adults does not reduce IQ or lead to problems with education.

British researchers assessed the relationship between the increasing use of marijuana among 15-year-olds and academic performance among 16-year-olds. The study was conducted on a sample of 2235 teenagers.

After eliminating interfering variables such as depression or smoking, which could affect the outcome of the study, the researchers said:

Those respondents who have had contact with marijuana at least 50 times did not differ in terms of IQ level and results achieved in science from those who never used it

Cigarettes smoking lowers general intelligence

Interestingly, a relationship was found between smoking cigarettes and weaker learning results – even after eliminating confounders. The data suggest that smoking contributes to lowering general intelligence and affects learning performance.

Researchers summarize:

The claim that marijuana use leads to lower IQ levels and learning disabilities have not been confirmed by the results of this study

In turn, a study conducted in New Zealand in 2012 and published in The Proceedings of the National Academy of Sciences indicates that frequent use of marijuana among people under 18 was associated with a lower level of IQ at a later age. An independent review of the study published later in the same magazine, however, claims that the study did not include disturbing variables such as socio-economic differences that could affect the outcome of the study, and the psychological changes of the subjects may not have any relation to the use of marijuana. .

Recent study results

A newer study published in Drug and Alcohol Dependence in 2015 suggests that:

The effects of long-term use of marijuana by teens are negligible compared to the long-term use of alcohol and cigarettes.


is a subject of much dispute in the research world.

For many years now, anti-marijuana activists have linked marijuana use with all sorts of negative outcomes. Some groups claim it leads to lower IQ scores. On the other hand, there are some (i.e. Dr Drew Pinsky) that have likened cannabis to dangerous opiates (technically, marijuana shouldn’t be classified under Schedule 1 (Class I) drugs).

A study in news coverage in 2014  seems to support the argument that cannabis is perilous for adolescents. Even though the available research may sometimes seem conclusive, scientists and research experts have not been able to prove the claim that marijuana leads to lower IQ and learning problems.


The results of individual studies are slightly different from each other and do not give a definite answer. However, many indications show that the occasional use of marijuana does not affect the overall level of intelligence and does not hinder the assimilation of knowledge in the future as shown in some studies.

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