• A new study says that using cannabis as a teen or adolescent can have negative impacts on cognitive functioning, especially verbal memory.
  • Researchers at the University of Colorado School of Medicine tested and analyzed siblings (unlike other similar studies) to rule out familial factors.
  • The study used interviews and neuropsychological tests to determine different factors and effects.
  • They found that using cannabis at an early age can lead to problems with memory, speech, and decision making.
  • In a time of increased access to cannabis with its legalization across the United States, more and more teens are using cannabis, which means it’s increasingly important that we understand potential side effects.
  • The research team says that more research needs to be conducted to better understand the relationship between cannabis use and cognitive functioning in teens and adolescents.

Quick Summary

A recent study “Familial factors may not explain the effect of moderate-to-heavy cannabis use on cognitive functioning in adolescents: a sibling-comparison study,” led by researchers from the University of Colorado School of Medicine, says that moderate use of cannabis during adolescence has negative effects on cognitive function. The study analyzed siblings, one using cannabis and one not, to rule out any familial factors. Past studies have not been able to do so. This new study helps us better understand what long-term challenges teens might face in their development.


Lead author, Jarrod M. Ellingson, Ph.D., assistant professor of psychiatry at the CU School of Medicine, says the team conducted the study to better understand if there was a link between early cannabis use and lower cognitive functioning. Researchers compared siblings to account for factors like…

  • Peer pressure
  • Parenting styles
  • Socioeconomic status

…which allowed researchers to better determine whether these were the cause of lower cognitive functioning or if the use of cannabis was to blame. With many teens and parents assuming that cannabis does not have long-term effects on development, it’s important to understand the full picture.


Over 1,000 adolescents were assessed through clinical interviews and neuropsychological tests. The teens were predominately male, making up 64% of the participants. Researchers also pulled teens from a wide range of backgrounds and ethnicities to rule out additional outside factors. Age, gender, and alcohol use were measured in addition to drug use. In past family-controlled studies, participants were infrequent cannabis users, only using 1-2 days a month. In this study, teens used cannabis on average 7-9 days a month. With cannabis becoming increasingly legal and accepted across the United States, there has been an uptick in use – such as among teens who have more access than ever before.


This study aims to help researchers, along with parents and teens, better understand the problems associated with using cannabis at an early age. After conducting multiple tests for each participant, it was concluded that cannabis use was associated with poorer cognitive performance.

Cognitive functioning is the internal mental processes that determine how people think, remember, speak, make decisions, and perceive things. The tests found that verbal memory was impacted the most, which is the memory of words and other abstractions involving language. One’s verbal memory is responsible for remembering what they read or heard and recalling it when needed.

The study also determined that poorer verbal memory performance was still associated with a greater lifetime use of cannabis. In conclusion, teens and adolescents who use cannabis starting at a young age may experience negative effects on their cognitive functioning that cannot be attributed to other risk factors.


The findings in this study clash with those of similar studies. The research team says that more research needs to be conducted to better understand the relationship between cannabis use and cognitive functioning in teens and adolescents.


Ellingson, Ross, Winiger, Stalllings, Corley et. Al. (2020, September 3). Familial factors may not explain the effect of moderate‐to‐heavy cannabis use on cognitive functioning in adolescents: a sibling‐comparison study. Wiley Online Library. Retrieved September 4, 2020 from https://onlinelibrary.wiley.com/doi/abs/10.1111/add.15207

(2020, September 3). Moderate Cannabis Use Impacts Cognitive Functioning. NeuroscienceNews. Retrieved September 4, 2020 from https://neurosciencenews.com/cannabis-cognitive-function-16963/

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Madison Bambini

Madison Bambini

Madison Bambini is a Communications Coordinator at Thriveworks. She received her bachelor's degree from VCU in mass communications, focusing on digital journalism and broadcast journalism. She also minored in gender, sexuality, and women's studies. Coupled with her love for writing, Madison enjoys producing content that is inclusive, empowering, and promotes the importance of mental health.

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