Summary: Yes, cannabis use can impair brain function in young adults.
Key Points:
- Chronic, heavy cannabis use is associated decreased activity in brain areas associated with memory
- Recent cannabis use is associated with poor performance on a variety of cognitive tasks
A New Era of Cannabis Legislation
Over the past 20 years, the cannabis legalization movement has changed the way people in the U.S. think about and use cannabis, i.e. marijuana, resulting in increased availability of legal, recreational cannabis, which begs the question we pose in the title of this article: can cannabis use impair brain function in young adults?
Consider the timeline of the cannabis/marijuana legalization movement:
- 1970s: 14 states decriminalize cannabis/marijuana
- 1990s: 21 states legalize medical cannabis/marijuana
- 2012-2022: An additional 20+ states decriminalize or legalize medical and/or recreational marijuana/cannabis
- 2024: Medical marijuana is legal in 38 states, while recreational marijuana use is legal in 24 states.
That’s why this question is relevant: marijuana is freely available to millions of young adults around the country, and the impact of marijuana use on brain function is critical to understand in order to safeguard the mental and physical health of young adults.
The paper “Brain Function Outcomes of Recent and Lifetime Cannabis Use,” published in 2025 in the JAMA Network: Specialty Journals of the American Medical Association, addresses the following related research question:
Are recent cannabis use and lifetime cannabis use associated with differences in brain function during cognitive tasks?
Let’s take a look at the study.
Cannabis and the Brain: Can Cannabis Impair Brain Function in Young Adults?
The research team identified the following goal:
To examine the association of lifetime history of heavy cannabis use and recent cannabis use with brain activation across a range of brain functions in a large sample of young adults in the US.
To accomplish this objective, the research team collected data from over 1,000 adults, age 23-36, and assessed the following metrics:
- Frequency of use:
- Heavy: 1000+ instances of marijuana use
- Moderate use: 10-999 instances of marijuana use
- Non-user: <10 instances of marijuana use
- Time of use:
- Past Month: recent use
- Lifetime use: ever used
Next, they assessed brain function using magnetic resonance imaging (mri), while participants completed tasks designed to test key areas of brain function, including working memory, reward, emotion, language, motor function, relational/logical reasoning, theory of mind, or how we understand other people by identifying their mental and emotional states.
Before we review the results, let’s look at the latest data on cannabis use in the U.S.
Cannabis/Marijuana Use in 2023: Facts and Figures
We collected the following data from the 2023 National Survey on Drug Use and Health (2023 NSDUH), published annually by the University of Michigan and the National Institutes of Health (NIH):
Past-Month Cannabis Use by Age Group: 2023
- 12+: 15.0%
- 12-17: 6.0%
- 18+: 16.3%
- 18-25: 25.2%
- 26+: 15.0%
Past-Year Cannabis Use by Age Group: 2023
- 12+: 24.9%
- 12-17: 14.7%
- 18-25: 36.5%
- 26+: 20.8%
Lifetime Cannabis Use by Age Group: 2023
- 12+: 47.1%
- 12-17: 13.4%
- 18-25: 50.0%
- 26+: 50.6%
Marijuana Use Disorder by Age Group: 2023
- 12+: 6.8%
- 12-17: 4.7%
- 18-25: 16.6%
- 26+: 5.5%
If we use the latest census data, we find there are around 22.5 million people in the U.S. between 18-25, i.e. young adults in the U.S. This means roughly 5.7 million used cannabis in the past month, roughly 8.1 million used cannabis in the past year, roughly 11.25 million ever used cannabis, and roughly 3.6 million have a diagnosis for marijuana use disorder. That’s why understanding this topic is important: it pertains to the long-term health and brain function of millions of people.
Le’s take a look at what the researchers found.
Cannabis Use and Brain Function in Young Adults: The Results
Spoiler alert: the data we’re about to share indicate that for specific brain function and specific types of use, cannabis impaired brain function. This data almost splits the difference between the two opposing – if anecdotal – points of view with regards to marijuana use that most people in the U.S. espouse: it’s either a dangerous illegal drug or a harmless substance we shouldn’t worry about. However, the data favor the group warning about the dangers of cannabis use: impaired brain function is serious outcome that none of us want for ourselves or anyone we know and love.
Here’s what the data show:
- Compared to non-use, heavy lifetime cannabis use was associated with lower brain activation on task that assessed working memory.
- Compared to non-use, recent cannabis use was associated with:
- Poorer but statistically insignificant performance across all tasks
- Lower brain activation on task that assessed working memory
The data offer a clear answer to the question “Does Cannabis Use Impair Brain Function in Young Adults?”
The answer is yes, cannabis use can impair brain function.
Recent use slightly impairs all brain functions assessed in the study and is associated with decreased activity/impaired function in brain areas responsible for working memory, while long-term use impairs brain function in areas responsible for working memory.
The takeaway here is that cannabis use, recent or long-term, impairs certain brain functions: we’ll keep our eyes open for more studies on this topic, and report any new information here.
