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• Posted October 30, 2024

Can Cannabis Change Your Brain? Maybe, Maybe Not

People who regularly use marijuana experience changes in their brain structure and function, but it’s not clear that cannabis is the cause, a new study finds.

Researchers found specific differences in the brains of people who’d ever used weed, particularly in areas densely packed with cannabinoid receptors. However, genetic analysis couldn’t pin down any specific association between cannabis use and these brain changes.

This means some other factor besides weed might be causing these brain changes in marijuana users.

“Our results need to be interpreted with careful consideration,” concluded the research team led by Saba Ishrat, a doctoral student in psychiatry with the University of Oxford in the U.K. “Additional research is needed to understand the effects of heavy cannabis use in this population, including considerations of potency and related information, to inform public policy.”

For the study, researchers analyzed data on nearly 15,900 weed users participating in the U.K. Biobank research project for whom genetic profiling and MRI brain scans were available.

Looking at the brains of the marijuana users, researchers found that they had poorer integrity of their "white matter," the part of the brain that connects different brain regions.

This was particularly evident in the corpus callosum, which serves as the main route of communication between the left and right sides of the brain.

Weed users also had weaker neural connections in the brain regions which make up the default mode network, which is thought to be active during mind wandering or daydreaming, researchers said.

However, heavy or long-term use was not strongly associated with any of these observed changes, researchers said.

Further, genetic analysis showed no significant association between a person’s cannabis use and these brain changes.

The new study was published Oct. 29 in the journal BMJ Mental Health.

“Cannabis users had significant differences in brain structure and function, most markedly for markers of lower white matter microstructure integrity,” the researchers wrote in a journal news release. “Genetic analyses found no support for causal relationships underlying these observed associations.”

It could be that some other variable like family history, diet or other medications might have influenced the changes, researchers said.

It’s also possible that the genetic analysis didn’t include enough people to be able to detect the effects of weed on the brain, they added.

More information

The U.S. Centers for Disease Control and Prevention has more on cannabis and brain development.

SOURCE: BMJ Group, news release, Oct. 29, 2024