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Does Weed Make You Stupid?

by Will Long

May 15, 2023
dried marijuana plant

Does weed make you stupid? The title of this article may read like a humorous question at face value, but it’s a legitimate question that many people have about the use of marijuana. As more U.S. states legalize marijuana for recreational and medicinal purposes, the debate surrounding its potential risks and benefits continues to grow. One concern frequently raised is the possible impact of cannabis products on cognitive function, particularly intelligence. 

We examined the existing research on the relationship between cannabis product use and intelligence to find an answer to this particularly fraught topic and explore the potential implications of these findings.

Does Weed Affect Intelligence?

What are the Active Ingredients in Marijuana?

Marijuana, also known as cannabis, contains over 100 active compounds called cannabinoids. The most well-known of these is delta-9-tetrahydrocannabinol (THC), which is responsible for marijuana’s psychoactive effects. Another notable cannabinoid is cannabidiol (CBD), which is believed to have potential therapeutic effects without causing a “high.”

Both THC and CBD interact with the body’s endocannabinoid system, which helps regulate various physiological processes, including:

  • Memory
  • Learning
  • Attention

They specifically “interface” with specific kinds of receptors in the brain that have both strong and mild effects.

What is the Impact of Marijuana on Cognitive Function?

There is a wealth of evidence suggesting that marijuana use can temporarily impair cognitive function. Short-term effects may include:

  • Memory problems
  • Attention issues
  • Information processing issues

However, the question of whether marijuana has long-lasting effects on intelligence remains unresolved.

Adolescent Marijuana Use and Cognitive Decline

A landmark 2012 study by Madeline H. Meier followed a group of individuals from birth to age 38, examining the relationship between marijuana use and cognitive function. The researchers found that those who started using marijuana in adolescence and continued into adulthood experienced a significant decline in IQ, with the most significant reduction observed in persistent users. 

This decline was not observed in individuals who began using marijuana later in life. This study suggests that marijuana use during adolescence, a critical period for brain development, may have long-lasting effects on cognitive function.

Read about the addictiveness of marijuana.

Marijuana Use in Adulthood and Cognitive Function

Research on the impact of marijuana use in adulthood on cognitive function has yielded mixed results. A 2016 study by Jared P. Reis found that while marijuana users performed worse on cognitive tests compared to non-users, there was no significant difference in the rate of cognitive decline between users and non-users.

Similarly, a 2018 review by J. Cobb Scott found that while marijuana users generally performed worse on cognitive tasks than non-users, the magnitude of these differences was relatively small. The researchers also observed an association between abstinence from marijuana and some improvement in cognitive performance, which suggests that the effects may be reversible.

Marijuana’s Likely Effects on IQ

Scott Alexander Siskind, is a popular psychiatrist blogger who’s written about a variety of psychoactive substances throughout his career. Siskind has concluded that there is likely some negative effect on IQ scores overall, especially on those who have used marijuana since adolescence. The average drop in IQ scores (a loss of ~8 IQ points) could have wider social effects en masse—perhaps raising crime rates. His ultimate conclusion is that legalization, for him, would pay off in the form of tackling organized crime around marijuana and decreasing a heavy use of taxpayer resources by law enforcement, freeing up their ability to deal with worse crimes.

Considering Confounding Factors and Study Limitations

It is crucial to recognize that various factors could influence the relationship between marijuana use and cognitive function. Socioeconomic status, intelligence, education, and other substance use could all play a role in shaping later cognitive function and potentially confound the observed results.

Additionally, many studies on this topic have limitations, including small sample sizes, self-reported marijuana use, and lack of control for potential confounding factors. The unfortunate trend of badly designed studies in the medical field has also further reduced the authority of studies that would otherwise potentially explain a major question in psychopharmacology. These limitations make it difficult to draw definitive conclusions about the relationship between marijuana use and intelligence.

The Importance of Future Research

Given the mixed findings and potential confounding factors, more research is needed. This might determine the true relationship between marijuana use and cognitive function. Longitudinal studies with larger sample sizes, better controls for confounding factors, and objective measures of marijuana use will provide valuable insight into this relationship.

The Bottom Line on Weed and Intelligence

Existing research suggests that marijuana use, particularly during adolescence, may negatively impact cognitive function and intelligence. However, study limitations and potential confounding factors prevent drawing definitive conclusions. With increasing accessibility to marijuana, individuals must become aware of the potential risks associated with its use.

If you or someone you know is struggling with substance abuse, including marijuana, it is crucial to seek help. There are numerous resources available to assist individuals on their journey towards recovery. Landmark Recovery is a leading addiction treatment center that offers a comprehensive range of services to support individuals in choosing recovery over addiction. 

Our team of dedicated professionals is committed to providing personalized care to help individuals overcome the challenges posed by substance abuse. Call us at 888-448-0302 to learn more about our evidence-based treatment programs and take the first step towards a healthier, more fulfilling future.

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About the Author

Will Long

Will Long

A graduate of Middle Tennessee State University, Long has been a writer for Landmark Recovery since 2021. He specializes in research and writing about substance abuse from a scientific and social perspective. Unearthing information from underexplored, far-flung corners of the Internet, Long’s passion is finding emerging trends in substance use and treatment that the public should know about.